SnapNDrag will let you do this. It's a very handy utility - I use it to capture images of particular windows most of the time, but it will do full screenshots as well.
For Windows using quirky keyboards, I tend to enjoy a little application called Capture. Lightweight (~210kb, I believe), the dev is a great guy and best of all it's free. You can also define a hotkey, and define different output options.
That said, the PrntScrn key is usually mapped to the F13 key. EDIT: I stand corrected. I was looking at my old black-key Pro Keyboard. It is indeed F14 on the white Pro Keyboards.