My program uses SHFileOperation to copy, move, rename, and delete hundreds of files. For most people, doing those steps to ~400 files takes under 15 seconds, but for some people it takes a LOT longer:
Timings at 08:11:20 Thursday, June 19, 2003
CModScript::Activate took 688.45 seconds (called 2 times)
SHRenameFile took 225.50 seconds (called 225 times)
SHCopyFile took 461.89 seconds (called 461 times)
SHCopyFile_SHFileOperation took 461.78 seconds (called 461 times)
SHMoveFile took 2.00 seconds (called 2 times)
Notice a pattern? Each operation takes EXACTLY 1.0 second! Another user having that problem had the exact same results, too, with SHDeleteFile also taking exactly 1.0 second per call. It isn't the users' computers' fault, either; they have similar specs to those having fast, normal times.

What could the problem be? This is a very confusing and unusual .