Ubuntu :: 10.04 Crashing All The Time?

I have Ubuntu 10.04 32bit on two machines and the one my parents has been crashing/having other issues a lot (the other is fine). I build my own PCs, and this one I built for my parents as a budget build as they basically use the internet and upload photos, that's it. It's got an AMD 64 3800+ processor, a GeForce 8400GS, 1 Gig of Corsair DDR2 (this passed 8 hours of memtest), an ASUS M2A-VM mobo and a 320GB WD HDD.

The crashes initially and may still be, GUI/graphics related. The biggest problem is they would boot up the system and there would be no GUI, it just never loaded so they would hard reboot. The other thing that would happen, when it went into screensaver mode, moving the mouse wouldn't bring up the password prompt, it wouldn't do anything just leave a black screen with no mouse, it would lead to a hard restart. These problems initially occurred on an older HDD that used to have windows xp on it that my parents loaded with viruses. Of course that HDD had been reformatted for Ubuntu, but I felt that it was damaged and these problems were related so I went and got a new Western Digital one for them and installed it with fresh installs of Ubuntu 10.04 (and a dual boot of Windows 7) but these crashing issues have persisted.

I found a fix on here that had me "force" the GUI to load each time via the terminal, which seems to have worked somewhat and the GUI loads more often. However, every now and then on boot up, parts of the GUI do not load and a window pops up asking that I delete elements from the panel. Again, this leads to a restart, except now sometimes when it reboots it gets to a DOS prompt (sorry, old windows user) of sorts that asks for a system password, when entered, nothing happens and requires another hard restart. These restarts tend to happen in chains leading to DOS prompt a faulty GUI or a GUI with missing elements.

There are also other general issues. Periodically desktop icons won't launch programs and or menu items will not load programs when selected, just nothing happens. When browsing the net with Opera or trying to open the recycle bin, the screen will just go black.I also messed around with the built in Nvidia Driver finder tool under system - administration-hardwaredrivers, tried the recommended and not recommended drivers, no difference. I've booted into recovery mode on the grub menu tried fixing and updating things via the menu options, still get one of the above issues.This system is up to date with system updates as well. I'm not sure what else to do, but I still have a sinking suspicion this is caused by some kind of graphics driver problem or maybe a problem with that graphics card in particular! I've installed Ubuntu fresh on this machine 3 total times, the latest install only last month when I created a dual boot with Win7.