system seems to have become corrupted

When I exit a games program my computer locks up.
When I try to shut down the computer it crashes and I get
error with various process particlarly symantec net
detect. Any thoughts on how I can fix this without once
again.. groan.. having to reinstall the whole system from
scratch.

What ever is wrong with my pc it seems to affected both
PCs I own in the same way. I cant shut them down without a
major error and I have to turn off the power.

I am running norton with latest definitions.
I am running latst free zonealarm
I have ALL microsoft updates
I have run lates spybot immunization
and I just tried running registry mechanic which found
many missing links but it did not solve my shutdown
problem.

I have seen people thruouh my high speed network planting
trojans before my eyes to spy on the pc without zonealarm
protection.

If they have also damaged my system is there a way of
repairing the problem? I dont want to restore because I
have changed much since it started happening.