Need help

Short concise background. Computer has been increasingly slower and slower. I was running (unhappily) The Shield, antivirus. I switched to Avast. Checked and corrected, spyware and malware programs, defraged, etc etc. Still slow and most recently on restart it came up in a different configuration, could not correct it or get it to come up in normal config.
Thought I would do a system restore. Well the system restore page comes up completely blank. All attempts to pull up through safe mode, etc. or to reinstall, have been unsuccessful.

Any ideas ??? What the heck happened ?? Virus ?

What do I do now ?