Computer restarting rigth after logging on

[prince harry]

For two days now my computer restarts right after I log on, every single time, it drvies me mad   

[THT]

This could be either software or malware/virus problem.

The first thing you should try is to turn off the autorestart option (Windows XP)

Right click the MyComputer icon, select Properties, open the Advcanced tab, clcik the Startup and Recovery Settings button
Un-check Automatically restart



See if you can log on to Windows now and do a complete virus and malware scan or see what software causes the problem.
If that doesn't work try rebooting in safe mode and run a complete virus and malware scan.