Windows XP logs on then logs off

Hello all,

My computer today had a virus. I tried to fix it by using several anti-virus programs such as NOD32 and SmitFraudFix.

After these applications had run and completed their full duration, I restarted the computer as it suggested.

The problem is, is that when it reaches the login screen and begins to login to the default account (User), it automatically logs me back out onto the login screen. The computer logs me out before I even reach the Desktop (Start taskbar etcetc).

Now, this is a repetitive process which keeps going. Login, and automatically logged back out. I have tried to login using Safe-mode and it does the same thing - logs me back out.

Atm I am on my second PC in the hope of finding help for this problem and I would appreciate any replies with guidance on how to begin resolving this problem.

Additional Info: I went away from the PC for abit 10minutes when it was on the login screen and came back. I clicked the user account and I could see an application running behind the Windows XP blue login screen so it seems that an application is running when the PC starts up or something which is preventing the PC from logging in fully.

Thanks, any help is much appreciated!