Need help and advise urgently!

My PC was working fine yesterday till I realised that I cant surf the internet. When I checked my modem, everything was fine but windows vista cannot detect the line. Then slowly I realised that some window services has stopped.

I restarted the PC but the loading was super long than usual. When the desktop finally loaded, there was an error msg that some services could not be started and prompted me to go to events log. I went there but said I do not have the rights but my log in is admin already. I also could not start services like windows update, windows firewall, etc.

I am suspecting that it is due to a trojan horse that my antivirus detected and removed. I did a full scan afterward but only found and removed some cookies thats all. after another restart, I cant even start my Macfee anitvirus now!

Please advise what I can do or the only way is to reformat....