Have not played far into FO3, but now whenever I bring up VATS there is only a 0% chance to hit any location. Makes no difference what distance or what weapon. pPoblem began before I added DLC (pitt, ancorage, point lookout and BOS). have loaded update to version 1.7. Is there anything I can do to get this to work. My laptop has enought memory (2GB), the right video card, but only runs at 1.6 GHZ vice the recommended 2.4 GHZ. It's playable but really need the VATS to get combat done.

Hi and welcome to the forums.
Have you already tried to set your GFX setting in the launcher to minimum? If you have only one core with 1.6 GHZ, you should decrease as much as you can, turn of AntiAliasing and choose the lowest resolution to play.

Other things:
Clean your system, close all backround programs (you might want to try a clean boot), perform a Windows Update, install the latest Direct X, disable Anty Virus Scanner & the Firewall as long you play ...

... and maybe, give the Game Booster a shot
http://thenexusforums.com/index.php?showtopic=111305

Had tried setting settings on low resolution, ect with no effect. Today, however I moved settings to med resolutions and vats mostly is working again. It seem to take changing resolution to kick start vats. At least I can now kill giant ants at a distance. Thank you for your help.