Dear participants
I'm using norton anti virus. It flagged me that my PC has been infected with Hacktool.Rootkit and then my PC works improperly. I have no idea how to deal with it. Please help me to eliminate this threat.
Helps will be much appreciated.
It noticed that file C:/WINDOWS/system32.dll was infected and delete or quarantine was failed.

I've never had a root-kit... WOW! lucky you!! I've run this a couple of times for boring, clean scan results. Go get it NOW.... cos the free version ends on Oct 1st. Tell us if it does the job - it's a rootkit scanner and removal tool.
Save it to a folder, put a shortcut to it on your desktop, start it and click Run and agree to license, next.. then scan. It will put a report in the folder you saved it to upon download.

One more thing, since Norton says you have the rootkit, lets assume that blacklight can fix the problem for you. So before you run blacklight turn off System Restore [via start > control panel > system > system restore - check the "turn off sys restore" box, Apply.... Do this because some rootkits come with programs that also infect system restore points, and windows protects these files from any scanning programs. Any restore point you have made while infected may be compromised. So you have to turn it off, clean if possible, then TURN IT BACK ON, and make a new restore point. Gee, i hope this works!
There is another free removal tool, UnHackme, from here:
Grab the evaluation version. Unhackme comes with a rootkit just so you can test out how well it works! Don't feel obliged to do this test... :)
Unhackme will hang around after you use it and check from time to time, but you can simply remove it if you wish.

Another route to System Restore, and the one you follow to actually use the thing, is this:- Start > all Programs > accessories > system tools > System Restore. The settings link there takes you to the same box as the route detailed above.