Prt Scr/Sys Rq or Print Screen will produce a .bmp the same as F5... or at least it does on my machine.
Just paste it into IrFanview to convert it (love that program). Best of all you can re-size while your there.
The thing about this subject is that there are so many ways to do this that it is up to personal preference, I used Wally for a long time, until atom sent me irfranview. I find it easier... but that doesn't mean that you will. The best fall back program is MSPaint, but it isn't as flexible.