It is a part of System Restore. You can reset system restore and then rescan and see if that does the trick. I find this odd that this just turned up and didn't show anywhere in the earlier Antivir scan unless is has to do with the original infection win32.Agent.pz which you said was removed. You never did say HOW it was removed by the way.

I am sorry here but I don't feel I have gotten the whole story in any of this. If this is some sort of game I would like to know. You post here saying that you cannot remove win32.Agent.pz which was found by Spybot. I ask you to run SDFix but you post back with a SmitfraudFix log, which I didn't ask you to run.Then you say thiswin32.Agent.pz is gone but don't say how.Then I ask, to be safe that you run the steps in PhilliePhan's sticky. You reply you ran those steps before posting the HJT log but you never posted any of those logs. Now you post back with the message that Antivir has found this other infection in your System Restore but it wasn't there or found on the machine before and it is not the same one found by Spybot and it wasn't found before by Antivir.
Sorry but I find this all odd and very frustrating.
Go ahead and reset System Restore.