Backdoor.tidserv trojan, help me please?

Norton 2009 detected the trojan backdoor.tidserv today.  When I tried to remove it, it said it could not be removed.  It recommended me to press “help” to link me to Symantec’s help page, so I did, and all of a sudden it said the issue was resolved.  I did a full scan, backdoor.tidserv came back up, wouldn’t remove, and disappeared whenI pressed help.  I then ran Malwarebyte’s Antimaleware quick scan, and it detected nothing.  I rebooted Windows XP in safe mode, and did another Norton full scan.  It didn’t detect backdoor.tidserv.  I checked the registry, no malware processes (I looked up which to delete).  I rebooted on normal mode again, and did another full Norton scan, the backdoor was detected and the same thing as before happened.  I couldn’t find it in the registry again.  What’s going on?  How do I get rid of it for good?  Why isn’t MBAM or registry picking it up?  Please help me!