I see. First I would try updating your graphics driver. Should this not help then I would do good deep scans for viruses and also malware on the computer to make sure they are not the cause.
After that we are getting into more complex issues. The next step I would try is running "chkdsk" (without the quotes) in the command prompt screen. The instructions for running it are below.
However, I would suggest you create a system restore point before doing this, just to be safe.
1. Go to the "Start" menu and then "Search".
2. Type in "cmd" (without the quotes).
3. From the list it gives right-click on "Command Prompt" and then select to use it as administrator.
4. Now when it loads you want to type in "chkdsk" (again without the quotes).
5. This will just check the disk but it won't fix anything.
6. The parameters for making any repairs, etc. using this command are:
"chkdsk C: /f" (without quotes) This option will attempt to fix any found errors
"chkdsk C: /r" (without quotes) This option will locate for bad sectors and recovery any readable information
"chkdsk C: /x" (without quotes) This option will force the volume you’re about to check to be dismounted before the utility begins a scan.
You can also run it using a combo of them or even all of them, like so... "chkdsk C: /f /r /x" (without quotes).
If the C: drive is in use, type Y to run a scan at your PC’s next restart. If so, exit Command Prompt and restart the computer.