SULFNBK.EXE

SULFNBK.EXE is an internal component of the Microsoft Windows operating system for restoring long [file name]s.

Email hoax

The component became famous in the early 2000s as the subject of an e-mail hoax. The hoax claimed that SULFNBK.EXE was a virus, and contained instructions to locate and delete the file. While the instructions worked, they were needless and can cause disruptions, as SULFNBK.EXE is not a virus, but instead an operating system component.
Even people who didn't receive the e-mail were still perplexed if they found the file by themselves, thinking that it could be a virus or trojan [horse |trojan horse].
In Windows 98 and ME, where the file existed, SULFNBK.EXE can be found in Windows "COMMAND" directory.
A very similar hoax happened with jdbgmgr.[exe virus hoax|jdbgmgr.exe].