[GalaxieFiveHundred]

Wow, reformatting the hard drive and reinstalling the OS
usually does the deal. Could be it's lodged in an email, program or website that you reaccessed after the cleanup.

[Stentor]

Wow, reformatting the hard drive and reinstalling the OS

Assuming that's what was done. I had one that put files in the restore partition so that the OEM restore process would have been compromised.