Corrupted desktop display, game crashing

[mash1971]

Hi, im pretty good with problems but this one is doing my head in now.
the problem is im not sure what the actual problem is.
the symptoms include corrupted desktop display, game crashing, corrupted firefox display.
these symptoms are not continual and dont appear after boot up.
ati smartgart reports agp is off, adjusting it makes no difference
the system is old but has been very reliable.
mobo is asrock 775i65gv with onboard vga
cpu dual core intel 2.8
mem 2gb
o/s xp pro sp3
graphics card ati radeon 9250 256mb agp 8
directx 9
all drivers are current including chipset drivers
things ive done.
reinstalled graphics card and drivers and onboard vga drivers.
ive tried using the onboard vga without the radeon installed but have same problem.
have disconnected all usb devices, but no change.
have tried 2 other hdds with xp pro o/s and still have the problem.
this makes me think its a hardware problem, mobo perhaps
have checked forums but no help.
anyone have any idea
any help would be appreciated
its got me baffled.
the worst symptoms are when trying to start games, and these games are old and according to their requirements this system is well above the recommended.
they recommend pentium 2 or above, thats how old they are,lol
oh and I have a superfast modern pc, but this one was the first I built so it has sentimental value, hence not keen on scrapping.

 

[terry5880]

1st 3 lines lead me to believe currupt grapics card might be wrong but desc top games etc all use graphics..
I do think its got something to do with graphics I could be totally wrong but seams very strange how mainly problem is when starting games. or maybe psu could be faulty and now supllying enough power lets see what the real tech guys say

 

[mash1971]

Thanks for the reply Terry, my first thought is that the graphics card is probably on the way out, its ten years old and was pretty cheap, but your point about the psu is worth investigating, its only 380 watts max and has to power 5 hdds, as well as everything else, so it might be that, I dont have a spare so cant check it as such.
the problem also affects skype when video is on, to the point where the video driver has stopped working, this I know because in the display settings it says that a supervga driver is installed and not the ATI one.
corrupted o/s perhaps
and I forgot to mention that the mouse keeps freezing, not the cursor the actual mouse.
one other thing im using a usb to sata adapter although even when its disconnected the problem still happens.
now when I use cubase (which is the most demanding software of all time) theres no problem.
could it be the Cpu, its a replacement I bought secondhand from ebay, last year, origin unknown, a sure recipie for disaster.

 

[terry5880]

It could be but doubt it I would of pointed to graphics card or psu