How to revert the compressed attribute on files in Windows for a whole drive

The compact /u command will do it. The PITA will be running it against all files, and you might want to preserve certain files compressed attributes, like c:\windows\$ntuninstall* . If you're not worried about the latter, just run compact /u /s c: and let it grind away and hope you don't run out of disk space.

If you have Cygwin installed, you could build a find | xargs compact /u with enough -name attributes to not uncompress directories that you want to keep compressed. You could also probably do the same thing with PS or (heavens) VBscript. A .BAT or FOR command is probably just asking for trouble.

It might also be best to let the IT guys do their job, or at least bring your concerns to them. It's not impossible to have a misinformed and/or junior IT guy do some unhelpful tinkering, do you have any IT guys that you trust at work?