WORM??? Any advice?

Currently running in safe mode, Ive been told Ive got a worm because of poor system performance and the signature nt authority countdown. Tried worm sweeper and get errors. checked system registry for two known worms with no luck, tried reinstalling and got STOP errors, what else can i do? Ive tried all that i can think of. PLEASE dont respond with FORMAT C DRIVE because if you know anything about computers you know its not possible in this situation