Henry, if you don't mind larger files, just hit the "V" key in FSX which saves a BMP.
I gave the commercial "Aerosohot" a whirl, which works fine as long as you're not running DX10 software. Ie. FSX in DX10 mode or Crysis, which it saves as a black screenie!
Sadly GrabClipSave, which I've used for years, didn't make the transition to Vista, it crashes often.