Due to the popularity of Progkill to many school and university administrators, and due to my lack of work on Progkill, I thought I'd pass along a link to some software that's probably more powerful than the current incarnation of progkill.
The software itself is called DeepFreeze (http://www.faronics.com/html/product.asp), and the Lab manager at the local community college where progkill got alot of testing at has leveraged DeepFreeze in a way that has been very effective in preventing student abuse of computing systems, and has saved the technical staff there quite alot of time.
The downside is this product isn't free like progkill, but for those looking for a really slick way of stopping students from abusing the machines, DeepFreeze (and probably even FreezeX) may be worth investigating.
--Kumba