Heres Symantec's info on that virus:
http://securityresponse.symantec.com/av ... pinfi.html
and McAfee's:
http://vil.mcafee.com/dispVirus.asp?vir ... structions
According to them it doesn't really do anything other than spread itself, they make no mention of a payload.
Its strange that it would be found in a .nltrack file, they say it only infects .exe and .scr files.
It doesn't do anything specificly nasty, but as you are noticing its spread will slowly degrade the performance of your computer.
I can't find any way to remove it other than buying some antivirus software. You could download one of the free trial versions from Symantec:
http://nct.digitalriver.com/0001/
McAfee don't seem to have any free trials, but they do have a free virus scanner
http://www.mcafee.com/myapps/mfs/ which would tell you if you have any other infections, and let you know how far this one has spread.