What did you use to clean registry? Most registry cleaners besides CCleaner are sales scams that have no genius behind them, and some can harm or even infect your computer.
First check for infection by downloading and installing Malwarebytes, update and run a full scan. Malwarebytes
Install, update and run a full scan with the best free AV: MS Security Essentials which is recommended by almost everyone here. http://www.microsoft.com/security_essentials/
Next check System Files by running SFC /SCANNOW Command - System File Checker
Google repeat errors in Event Viewer>Admin View to see how others have resolved them.
Run the memtest suggested earlier, then test your HD using maker's full repair CD scan: http://www.tacktech.com/display.cfm?ttid=287
Consider a Repair Install
as a last resort before clean reinstalling.