sorry for the late reply. I have been very busy these few days
These symptoms aren't caused by malware.
Put the Windows CD into the computer.
Open the Start Menu > Run.
At the prompt, type:
It will check your system files and replace them where needed
At the end it will tell you the result, please post it here
Try now with MBAM and tell me if it still crashes.
Check your computer and tell me if the symptoms you described above are still there