ive been trying to create some new screenshots from in game. all my efforts i end up with desktop screen pics. i have windows 8 any ideas ?

Take Screenshots with Fraps or run GTA IV in windowmode. I personally prefer the solution with Fraps.

will i have to record the game first or just take snap shots ?

You run FRAPS or bandicam or another program of the sort while you are playing gta and use the screenshot hotkey. This will give you a screen shot in game

You can also use Steam to take screenshots.  Even if you're using the disc version, you can still use the Steam Overlay to take screenshots.  Or, you can use FRAPS or Bandicam, as mentioned above.  I prefer using the Steam overlay personally.

Are you using the Print Screen function? If that's the case then all you have to do is disable the Aero Glass effect. I know it works for Windows 7 but you can try with your Windows 8.