Well the visual settings for the game would have to be set fairly low for you to play Gears of War and achieve a high and stable framerate with your PC spec's.
- The system requirements for Gears of War:
OS: Windows Vista or Windows XP
Processor: 2.4+ GHz Intel / 2.0+ GHz AMD
Memory: 1GB RAM, 12GB free hard drive space
Video Card: NVIDIA GeForce 6600+ / ATI X700+