tape recording

Is it legal for your boss to hide a tape recorder in your office without your knowledge?

Normally that is not allowed and it can be a criminal act.

I recommend you also check with your state attorney general's office or the local police dept. --See also "taping phone calls" -- http://www.worldlawdirect.com/article/1042 -- if you can't tape calls then you normally cannot tape conversations--if you can tape calls then check with your State Attorney General for the laws regarding in-person conversations--