Windows 7: Win 7 Performance

Hi there, i've both 32bit xp sp3 and 32bit win 7 rtm installed. I just bought Red Faction Guerrilla game..i run the game both with xp and win 7.
But there are lots of graphics issues with win 7. First of all, its kinda slower than xp..and fps is getting too low when there are too many objects(particles and stuff) in the game...
I have an Ati 4870 512 mb graphics card with latest 9.9 drivers..
Does anyone have any solution please?

You may need to wait for the first official patch - fixes which may interest you:

• Sometimes using anti-aliasing on certain ATI cards causes weird flashing\tearing. Disabling anti-aliasing may fix these issues before the patch, but the patch will correct this issue.

• Several crashes for users running ATI cards have been fixed (most often when accessing Display Options in game)

• Performance improved on ATI cards

No release date on the patch yet, but you can keep an eye out here if you want:
Upcoming PC Patch Details (Date TBD) | Red Faction Underground