Heeeeeeelp

i Keep getting a Winlogon.exe Error Msg comibg up then the BSOD (Blue Screen of Death)

Can work out what needs doing, Tried runing Adaware but this just causes system to crash during search... My Virus Software finds nothing.

And of you PC wizards got any ideas, as mine only strech to Format the whole Hard drive and reinstall everything or chuck it out the window