[TopAce]

My computer has had problems with booting up ever since I got it two or three years ago. When I press the power button, the comp seems as if it started up like normal. However, within moments (seconds at most), everything goes silent. The LEDs turn off and the fan stops.  I just had to try again and it would work. It wasn't a serious concern because it happened very rarely. Yesterday my comp has practically died on me. It just wouldn't start, so I started doing some maintenance, cleaning the chassis (which I do rather frequently) and making sure every peripheral was properly plugged in. The problem remains.

I have a number of suspects

The video card (GeForce 7600 GT) needed an additional connector for some more juice, otherwise it wouldn't work. I'm having a power-related problem, so I removed the connector to see if it will solve the problem. It didn't.

The power supply. I replaced the old power supply with a new one, cable included, but no luck with that either. Both are 300 Watt.

The motherboard (ASUS P4P800) and the initialization mechanism are the remaining likely suspects. The motherboard could be responsible, because it seems that if the video card or the sound card is a little bit out of position (I don't at all mean unplugged here), the computer will not boot. The machine simply stopped once as if there were a power outage, and it didn't reboot until I replugged the video card.

I'm thinking of buying a new motherboard (with chassis) if nothing else works, but I'd like to hear your ideas before spending any money.

[Klaustrophobia]

my first thought is power.  are you sure 300w is enough? 
check for damaged capacitors (bulging on top, leakage, corrosion)
reset CMOS to default.

those are the best 3 ideas i have.

[TopAce]

my first thought is power.  are you sure 300w is enough?

It must be. If it weren't, the comp wouldn't have worked for years.

check for damaged capacitors (bulging on top, leakage, corrosion)

No physical damage is discernible.

reset CMOS to default.

It's default.

[Klaustrophobia]

my first thought is power.  are you sure 300w is enough?

It must be. If it weren't, the comp wouldn't have worked for years.

you said this was present from day one and got worse recently i thought.  i'm no electrical expert, but i would imagine an aging system with degrading contacts stuff (you mentioned reseating components affected it) could exasperate the problem if it had been teetering on the edge.  this is still just a guess.

if you get to the point of buying new parts, maybe try a better power supply first and move on to the other stuff if that doesn't fix it.

[pecenipicek]

reset CMOS to default.

It's default.

pop the battery out for a few minutes, and while you're waiting, check the voltage, if it isnt around 3V, replace it. the battery type is CR2032

[Tyrian]

My vote is for a power + mobo combination.  Could you post your full specs and if you're OC'ed at all?

My guess is something along these lines:  You may already be close to your PSU's power ceiling.  I'm assuming that you have electrolytic capacitors.  The average lifetime of one cap is about 1000 hours, if your caps are cheap.  However, your system is 2-3 years old.  If you leave it on a lot, then it's probably run for 12000 to 18000 hours, based on the age of your system and assuming you leave it on for about 16 hours a day.  The problem is that as caps age, the equivalent series resistance can go up, sometimes by a lot, if the caps are cheap.  That sort of decay leaves no physical evidence.  Greater resistances can increase power losses in your system, moving you closer and closer to your power ceiling.  One way to check it would be to pull as many peripheral cards as you can and run off onboard systems.  If you see greater stability, then you know it's a power issue.

[pecenipicek]

My vote is for a power + mobo combination.  Could you post your full specs and if you're OC'ed at all?

My guess is something along these lines:  You may already be close to your PSU's power ceiling.  I'm assuming that you have electrolytic capacitors.  The average lifetime of one cap is about 1000 hours, if your caps are cheap.  However, your system is 2-3 years old.  If you leave it on a lot, then it's probably run for 12000 to 18000 hours, based on the age of your system and assuming you leave it on for about 16 hours a day.  The problem is that as caps age, the equivalent series resistance can go up, sometimes by a lot, if the caps are cheap.  That sort of decay leaves no physical evidence.  Greater resistances can increase power losses in your system, moving you closer and closer to your power ceiling.  One way to check it would be to pull as many peripheral cards as you can and run off onboard systems.  If you see greater stability, then you know it's a power issue.

or to get a power meter and plug it in a wall outlet before the PC itself and see if the overall power draw is close to the 300W.

[TopAce]

If you leave it on a lot, then it's probably run for 12000 to 18000 hours, based on the age of your system and assuming you leave it on for about 16 hours a day.  The problem is that as caps age, the equivalent series resistance can go up, sometimes by a lot, if the caps are cheap.  That sort of decay leaves no physical evidence.  Greater resistances can increase power losses in your system, moving you closer and closer to your power ceiling.

Amusingly, my older machines lasted a lot more than this current one, and I haven't had any issues with the PSU yet.

One way to check it would be to pull as many peripheral cards as you can and run off onboard systems.

I tried unplugging the video card, which theoretically is the most power-consuming peripheral in my rig. Maybe not the most consuming, but a consuming one nonetheless.

you said this was present from day one and got worse recently i thought.  i'm no electrical expert, but i would imagine an aging system with degrading contacts stuff (you mentioned reseating components affected it) could exasperate the problem if it had been teetering on the edge.  this is still just a guess.

"Recently" in this case means "abruptly overnight." It was all fine the day before yesterday, but yesterday it stopped working. It there had been a gradual degradation period, I'd have likely found the problem and began remedying it already.

Now that I think of it, getting a better power supply may be a good idea, considering that if I buy a newer motherboard, I will need one anyway.

[TopAce]

(accidental double post, sorry)

[zookeeper]

Sounds rather unlikely in your case, but doesn't hurt to mention that just a couple of days ago I too had a problem powering up my machine (it turned on, ran for a couple of seconds, then turned back off on its own), which luckily ended up being nothing more than a mechanical problem with the power button.

[S-99]

The video card (GeForce 7600 GT) needed an additional connector for some more juice, otherwise it wouldn't work. I'm having a power-related problem, so I removed the connector to see if it will solve the problem. It didn't.

The power supply. I replaced the old power supply with a new one, cable included, but no luck with that either. Both are 300 Watt.

I use to have that video card, and a 350w psu. I bought the 350w because it was what the video card manual said was the minimum power requirements (and to save some money). Wrong, I had the same problems as you. It got to the point where my computer would not be able to be on for more than 8 hours. The problem got fixed when i tossed a 450w psu in the computer. That gave the video card more than enough power (i assume a 400w would do the job, but wanted to be sure so 450w).

[TopAce]

450 W? Woah. I thought my 300 W would do the job.

Thanks for the info, all. I suppose my question has been answered.

[LHN91]

450 W? Woah. I thought my 300 W would do the job.

Thanks for the info, all. I suppose my question has been answered.

Just wanted to make a quick side note here. If you're going to buy a new power supply, I would recommend starting at a 500w and looking at 600w. 500w is *just* enough to run my current system, and it's nothing particularly special. Just for a bit of future proofing and wiggle room later on.

[Fury]

There is a huge difference between a good quality PSU and ****ty PSU of same wattage. Always make sure to buy good quality PSU and not cheap garbage even if the difference on the box is 500W.

Just wanted to make a quick side note here. If you're going to buy a new power supply, I would recommend starting at a 500w and looking at 600w. 500w is *just* enough to run my current system, and it's nothing particularly special. Just for a bit of future proofing and wiggle room later on.

IMO that'd require complete system rebuild and such high-wattage PSU would be wasted. Better get good quality PSU instead, even if a bit lower rated wattage.

[LHN91]

There is a huge difference between a good quality PSU and ****ty PSU of same wattage. Always make sure to buy good quality PSU and not cheap garbage even if the difference on the box is 500W.

Just wanted to make a quick side note here. If you're going to buy a new power supply, I would recommend starting at a 500w and looking at 600w. 500w is *just* enough to run my current system, and it's nothing particularly special. Just for a bit of future proofing and wiggle room later on.

IMO that'd require complete system rebuild and such high-wattage PSU would be wasted. Better get good quality PSU instead, even if a bit lower rated wattage.

Meant to say this as well, and didn't. However, the OP seemed like he might be thinking of an upgrade soon anyways, that's why I suggested it. Check reviews, read the detailed specs, look for good names, etc.

I just feel like, IMO, a decent 450 or 500w power supply, with a strong 12v rail is the minimum if you don't want to buy a new power supply again the next time you upgrade anything. And that aside, having the extra breathing room of a 600w is nice to have, if you find a good deal on a quality one.

[S-99]

450 W? Woah. I thought my 300 W would do the job.

Thanks for the info, all. I suppose my question has been answered.

Yeah, i thought my 350w would do the job too. But yeah, do what other people recomended. Get a good quality higher wattage psu you can also use in a future system.

[deathfun]

My initial thoughts were actually the heatsink not doing as it should
I've had a computer with a similar description for an issue, would start it up, then moments later it just immediately shuts off. Heatsink turned out to be the culprit

[Klaustrophobia]

if you go for a high-quality PSU you're probably going to end up with higher wattage as well.  the companies producing the high quality stuff are going to tend to target the high end hardware market where it seems 600w is the latest "normal."

hardwaresecrets.com has very detailed PSU reviews that are good for finding out exactly what models are high-grade.  newegg seems to have power supplys on sale all the time.  i got a $200 unit for $89 after rebate.

[Nuke]

id check out the psu rout myself. especially if its the psu that came with your case, those kinda suck.

[Nuke]

reset CMOS to default.

It's default.

pop the battery out for a few minutes, and while you're waiting, check the voltage, if it isnt around 3V, replace it. the battery type is CR2032

ive never seen one of those die before the computer became obsolete junk. if it did, your bios would just reset to default every boot and you would get a cmos memory fail message.