Virus log off and switch user to system

I think I am hit by one or more virus.
1. It can not be removed by Norton or antispyare;
2. It is activated after connecting to internet;
3. It starts some process and applications;
4. It changes registry;
5. It changes services
6. It takes over the PC and log in as System;
7. It creats a lot of programs in root directory of drive c, maybe other sites I do not know;
8. The programs takes up all CPU resources;
9. PC hang..........

Anyone can give me some suggestions? Please HELP