1. Machan..check for Blue Screen....If so remove the ram and plug it again....( If it is the RAM :- remove it and use and Eraser and rub off the pins on the either sides below where it is fixed to the slot......)
If blue screen does not come or not an issue with the RAM got to 2.
2. When the computer starts...Press F8 and go to advanced Options and select Directory Services Restore....And after coming to windows shut down and restart windows Again
After Restart Run a Scan Disk....and Defrag the Hard means C:
3. There might be possibility of a virus attack upgrade ur Antivirus and and use some tools to check it thorough
3.If all the above does not workout better format the Cr partition where windows is and then repartition it to make two ans install windows to one of it...will fix the prob.