is there error pops-up? if any can you specify one?
what is the video card you have?
their might be compatibility issues with win7 64bit try updating you video card
Try this one:
1. Go to your Steam Games Library.
2. Right click "Sniper: Ghost Warrior".
3. Select "Properties" in the drop down menu.
4. Navigate to the "Local Files" tab.
5. In the options below, click "Verify integrity of Game Cache".
This will replace/download any missing or corrupt files.