Hi there s0nIc!

This threat is quite old. It could already infected the system hard and down to the registry.

Check this complete information and instruction from Symantec - Backdoor.Trojan http://securityresponse.symantec.com...or.trojan.html

Since the OS is Win XP, you can find more technical information about the situation here - Common loading points of threats in Windows 2000/XP http://service1.symantec.com/SUPPORT...01060517115206

WARNING: Symantec strongly recommends that you back up the registry before you make any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify only the keys that are specified. Read the document How to make a backup of the Windows registry for instructions.
Hope it could help.

-GONE