I'm looking for a software for Windows XP or a mechanism within Windows XP that will allow me to automatically lock Windows (same effect as WinKey + L) at a given time (e.g. at 3:30 pm) or after certain timer expires (e.g. 15 minutes).
I'm going to take an interview and the interviewee will be assigned fixed amount of time to solve some programming problems with PC. I like the PC to be locked after that time has elapsed.