Command line w/Win7 x64

Trying to schedule a defrag task in Win 7 x64 - wondering which .exe to use. Probably doing something wrong, but I don't see much happening with either one, although df.exe did show up in Task Manager long enough to see it, then close a split second later. The documentation doesn't mention df64.exe, just df.exe.

Is there some logging I don't know about?

With thanks

EDIT: OK answered my own question. df64.exe was working just fine, but my drive is defragged enough that the .exe didn't have to run long enough to even see it. Found that out by quitting the lazy and headed to the command line...

df64.exe. The 64 part denotes that it is for 64-bit systems.