[Hellstryker]

My computer freezes when it says "Boot from CD/DVD:" or whatever it is exactly if I have a DVD in the drive... never happened to me before 

[FUBAR-BDHR]

I've had a few machines over the years do this.  Some of them had the CD/DVD player going bad.  Some had a floppy drive go bad and the boot sequence set to CD/FD/HD.  Some older machines even had BIOS problems that would cause this.  Probably not the case unless it's a really old machine.  I think there are even drives that wouldn't boot with certain types of CD or DVD's inserted.  Like a music CD instead of a data CD or a non bootable CD. 

Does it do it with all CD/DVD disks?

[Hellstryker]

Not sure, I really don't have much to test with, and it's a DVD only drive. The thing is, i've had the same DVD (Sup Com) in with no problems up til now. The system is pretty new, although the DVD drive is going on 4 years I believe, though I hardly ever use it.

[FUBAR-BDHR]

Try another DVD even if it's blank or one you burn yourself.  Also check the DVD that was in there to see if it's dirty.  I've had them get a grayish film on them from being in the drive forever.  It could be interfering with the boot sector and confusing the system by making it think it's bootable.

Also check your BIOS and check the floppy drive setting even if you don't have a floppy.  Most systems will default to A: being a 1.44 floppy and search for it at boot.  Had that happen just yesterday with that messed up system.  BIOS reverted to the 1.44 drive installed when it doesn't have one.  It hung on the SCSI config screen until I disabled that drive. 

If the drive works fine otherwise and you don't use if for booting try disabling it as a boot device.  You can always enable it if you need to reinstall or something.  Just remember you did it.