Virus?

My computer constantly gets blue screen errors, all programs are corrupt, as is anything downloaded. All programs give errors and shuts down.
screen flashes on and off. Nothing will install. USB not accessible
When attempting online scans an error will appear and the browser shuts down.
Sometimes when starting it gives an error that the windows reg. has been edited and fixed and asks for win cd to replace files that had been changed.
All of above has happened in safe mode too.

Hard disk had been reformatted and problems reoccured.
Virus scanner would not run nor the online scanners.

Ran Hijackthis (it ran) and saved the log.
Does anyone know what the heck is happening???