Is my computer being hacked?

[Qal]

My computer, with windows xp pro, already has norton
antivirus and a firewall. But I have a feeling that it
may've been compromised by a hacker. Is there any way to
find out if a hacker is accessing my computer. All the
tests I have conducted on the ports and for worms and
trojans returned negative. Can a hacker install a
programme and conceal it as to fool all those tests. How
do I find out for sure? Thanks

 

[David Jones]

Anyone with physical access to a computer can 'hack' it.
However, you're doing all the right steps, and it is
unlikely that your machine is hacked with the protections
you have in place.

Why do you have the feeling it may have been compromised?

 

[John Smith]

Qal,
If you've been using it for three years without a wipe and reload it
probably will act weird. In my opinon you should do a clean install of
Windows every year to keep it clean.