Does PC have a trojan/virus?

Help
Currently have Norton Protection (Virus/Firewall) installed on Dell Dimension XPS T500. PC has intermittent "clicking" sound coming from HD. Had this onece before and discovered that it had a trojan. Used McAfee to clean it. Virus scans show no infection. Is there another reasonf or the clacking sound? Was told it was registry files trying to write to the HD. Correct or not? Any suggestions on getting rid of it?

 

No virus.
I believe.
My guess is a defected HDD.

 

Defective as in probably needs to be replaced?

 

yes. backup any important data now. and start looking for a new drive.

 

you should update you virus program and then if it still doesn't come up with a virus get a new HDD.

 

Norton Virus Protection and Norton Firewall are new (less than 6 months). Had McAfee prior to that.
Maybe I should have explained myself better. The sound I am hearing from the hd is that of a relay opening and closing. When this happens, the pc pauses whatever it's doing and proceeds only when the "relay" stops.
Additionally, cannot open .wmv files without pc shutting down and re-booting. Is this related - not enough oomph to process wave files? Use Windows Media for this.
Have defragged/optimized several times. Also, cannot run chkdsk /r without rebooting. Keep getting an error that says "volume is in use by another process". Is Norton preventing it from running or is there something else going on? Lots of questions, but need HELP!!!