This can be either your hardware or software playing up, it can be difficult to test what it is.
One thing you can do is go to http://www.memtest86.com/ and download the software and burn it to a CD using a ISO burning program and boot your pc from the cd. This testing could take long and maybe you should read up about it a bit first. But in some cases it is the RAM that gives the error and the RAM can simply be removed and replaced and other cases may be a bit more bad.
There is also cases where it might not be hardware at all. I'm not too familiar with Software errors in this case but I know one test you can do is the following:
Before you do this go read up about it here:
http://www.sevenforums.com/tutorials/1538-sfc-scannow-command-system-file-checker.html
-Locate your Command prompt (cmd) file (Shortcut will work as well)
- Right click on it and run it as administrator
-Now type SFC/SCANNOW and let the test run and see if you get any errors
Hope this helps