CCleanr foud it here:C:\Documents and Settings\User Name\Local Settings\Temp\ztf88z2.dll
But Cleaner can't delete it. I tried Unlocker, still can't delete it. It can be deleted under Safe Mode, but shows up every time I restart Windows. I also tried anti-virus softwares, they found nothing. I can't find any informations about "ztf88z2.dll" on the net. What's up??
Use Delete FXP Files. It will delete anything you can throw at it regardless whether the file is locked or being used by another application or process. And that's in normal Windows mode.
I never heard of ztf88z2.dll and that fact that you said it recreates itself on startup in Local Settings/Temp is very curious.
You may want to use a combinaton of Filemon, Process Explorer, Regmon - all by Sysinternals - and Dependency Walker - to trace the dll to the executable and process that use it.