scanning a computer remotely for spyware?

[fafster]

One of the teachers managed to stumble on to www. caravan-dealers.com (broke the link on purpose) which hosts spyware. I need to check if the machine has been infected, so I thought why not also do the same for other workstations.

 

What's the best way to do this remotely/centrally? Ideally it would be a free tool, but if it's worth paying for then it would have to be considered.