I would look at replacing the video card.
The problem i'm having is the PC restarting during startup, "Windows is starting", just before the welcome screen. Choosing startup repair on a subsequent go around brings me back to the boot menu (I have ubuntu loaded within windows). I don't know if the same will occur when booting ubuntu but once again it's installed in windows 7 as a program. Now using the Win7 32bit recovery disk, I can do a chkdsk /f and the next time I boot it gets through startup and I can log in. However, when I shut down and boot it up I run back into the problem again.
Putting the PC to sleep puts it into an unresponsive state requiring me to hold the power button to shut it off. Also the PC went into its unresponsive sleep state about a half hour into Fallout New Vegas, when I restarted and opened the game it went into its unresponsive sleep state about 30 seconds after opening the application. Oddly sound still worked and I could hear the game's menu music.
This problem started four months ago but its my sister's PC and I've only been back for a week. The PC had been off for that time and doing chkdsk /r using the win7 recovery disk seemed to bring the PCback to normal. However, the problem magically resurfaced yesterday. Its had plenty of use over the week and handled BF2142 fine for hours despite putting itself to sleep during Fallout.
Also sometimes during bootup letters are missing from words (eg my PNY Verto graphics card is shown as P Y Ve to during boot), text is in green or pink or both, screen is covered with green or pink or black lines. Whenever those things occur it almost always means it wont get to the welcome screen. Occassionally I get to the welcome screen and log in, but the screen goes blank and never reaches my desktop requiring me to shut off the PC. This is slightly different though because the pointer is on the screen and functional but the screen remains blank and the only option is to hold the power button and shut it off.
Any help is greatly appreciated. It's an Acer Aspire M1100 with 3 GBs of RAM running 32 bit Windows 7, the video card is an NVIDIA GeForce 8500 GT.