When I run my ESET antivirus V4 I immediately get "unable to clean Win32/Rootkit.Agent.ODG trojan. I think it is a boot sector virus. I can open web pages, but I am unable to update my NOD antivirus or download any files from the Net. Hijackthis fails to install - when I hit RUN HJthis just dissapears? Also, Adaware Anniv Ed finds and quarantines a threat called Win32Backdoor.TDSS, but Adaware keeps discovering it next time the PC is restarted. Can you advise me about removing the rootkit threat and the backdoor trojan. Should I try a "Clean Boot" to minimise what processes and services are running? ++++++++++++++++++++++++++++++++++++ 02 June 2009....... Thanks very much for your replies and help. I did connect the HD as a slave to another PC and scanned with NOD and Adaware Ann Ed. The rootkit and other debilitating threats have now been removed. I shall now get familiar with some of the tools mentioned, eg rootrepeal, The Avenger, Combofix, Malwarebytes.