[Bob-san]

I would not try to restore any registry or whatever. Since the first installation had problems and then you installed on top of that, It sounds very messy 

Since you have gone into all the trouble of trying to fix it why don't you just finish the job?

1: back up EVERYTHING you need to a USB / CD, (also do manual search into every folder for misplaced files, the desktop etc etc)

2: find the VISTA cd and the MSoffice cd making sure you have all registration info.

3: install VISTA but this time ask it to REFORMAT your hard disk (if the previous installation if full of viruses etc I would not even trust it to put the old data in the a folder)
   unless you have a VISTA upgrade cd rather than a full installation cd, hence out of luck

4: run all the updates and install all the drivers as needed

5: get a copy of an antivirus, I use AVG (free and seems ok)

6: install office

7: have a nice hot chocolate

AVG is all well and good for online link scanning, but just doesn't cut it as a true antivirus IMO. I recommend MBAM, or if your parents think the only way to protect your PC is by dishing out enormous amounts of cash, NOD32 or Kaspersky.

I've never had a problem with the red umbrella--so I'd have to say take a look at Avira.

[ShadowGorrath]

So where can I find the registry file/files? Just tell me, I'll risk it.

[Jeff Vader]

AVG is all well and good for online link scanning, but just doesn't cut it as a true antivirus IMO. I recommend MBAM, or if your parents think the only way to protect your PC is by dishing out enormous amounts of cash, NOD32 or Kaspersky.

I've never had a problem with the red umbrella--so I'd have to say take a look at Avira.

avast! Install it, run a boot-time scan, kill everything that seems even remotely suspicious, be happy.

[ShadowGorrath]

Ok, ok.... Away from antivirus programs and on to fixing Office.

Ok, so what should I do? I don't want to resort to downloading and reinstalling...

The error it gives when I try to launch it says: "Not enough disc space or memory" or something like that.

[dr_costas]

So where can I find the registry file/files? Just tell me, I'll risk it.

I am not sure you actually know what you are doing. Have a read at this

http://www.argentuma.com/backup/registry-backup.html

the registry is just a database incorporating the values stored in many different files. If you mess with it you risk ending up with the computer not starting at all. If nearly died of horror because the computer was not working properly once you interfered with it, you will die for sure if it will not start at all. It is much safer and easier to follow my advice above as long as you have backed up everything and have all the disks you need. If not, then run a registry cleaner and an antivirus and reinstall the MSOffice (unless you don't have it)

i hope you sort it out, I have been there before many times  

EDIT: you posted while I was writing. Check how much free space you have on your computer. Go to My computer find c drive and right click - properties. It may be that you have run out of space and vista is complaining,

[The E]

OR, Word needs some Registry settings it isn't finding. I'd still recommend reinstalling.

[ShadowGorrath]

No! There's enough memory ( 2GB RAM ) and enough disc space ( more than half the hard drive space ).

And yes, Word needs some registry entries, I'm almost entirely sure of that. But I can't find it. If I could reinstall Microsoft Office programs, I would have already done it. Otherwise I'd have to download them, and I don't want to resort to that...