On all of my keyboards, the print screen button is on the Sys Req button. Regular press is Sys Req (which is the print screen button in the tree editor) and if I want to do a windows print screen I have to press shift.
On my keyboard it's the opposite, actually. Print Screen is the first option, and under it is the Sys Req, so I'd have to hold shift and press it to get the Sys Req.