NAIL.EXE won't go away
A filed named C:WINDOWSNail.exe indicates that you have a spyware infection named Aurora. It's evil. A user cannot delete nail.exe, because it just comes back. It can be removed by a technician, but it takes a lot of time analyzing the memory threads that Windows loads.
JK TECH WORKAROUND: Techspot has an excellent article here. We have used their manual method and Nalfix to fix the problem