I think i have a virus :-(

Hi

I am new to this as never had this problem, my computer started running very slowly and hanging, the hard drive was constantly running, cpu usage 100% and 123 processes running.

Then norton internet randonly turned itself off and on, the stopped working. I tried to reinstall norton thinking there was a problem, but it will not re install bringing up the red error box. I ran power eraser, but after removing some rubbish it still wont install. So i have spent the evening running the norton recovery boot tool, it scanned everything and didnt find anything.

Norton still wont install, what can i do now ???