I need to run calculations on school computers that run Windows XP. It's going to take a while (few hours) and I don't want to constantly be "babysitting" them to make sure they don't go on standby. I'm therefore looking for a way to trick the computers into thinking there's an active user, or some other way to reset the user idle time. Bear in mind I don't have admin privileges. Any suggestions?
1) Depending on how well the IT staff is at your school: Ask them. I rarely had problems with IT if I asked a reasonable question with good arguments as to why I needed it.
1b) Get a teacher to keep moving the mouse. (S)he will call IT in no time.
2) Borrow a USB device which continuously generates some input. They exist, but unless you happen to know someone which has them or already own one it will take time and money to get one.
3) Do to thing I will not advice on S.U. and modify the power options with admin rights. Often the quickest and easiest way, but IT will not like you if they discover this. Try asking them first.
4) Not sure if this still works: Start mediaplayer. Older versions of XP had a 'broken' mediaplayer which prevented the system from starting a screen saver when the media player was running. I realise that a screen saver and standby is not quite the same. But it is worth testing.