Games won't launch on my new Windows 7 32-bit partition on an iMac.

What you stumbled upon is probably the manual update feature inside the Device Manager you tried to run. Windows reported that you have the latest driver version, and that is true, but those drivers are generic and cannot actually control your hardware, hence the low score on the WEI. To fix this, like we already mentioned, just figure out which GPU you have and download the appropriate drivers from the hardware manufacturer. Once you install them you can rerun the WEI test and you'll see a vast improvement

Yep your correct once we can get a confirmation on the graphics your mac is running we will download the REAL graphics driver. Currently your using generic graphics drivers which is why it shows your graphics as VGA. This is my hypothesis anyways. As soon as you can let us know which model or graphics your I-mac came with i can direct you to the appropriate drivers. If i randomly give you to try out you could come up with all sorts of weird problems later on or nothing may happen at all.

Great! Post back if you're successful in installing them and if the games are running properly.

I'll look it up for you and edit this post with the link...

EDIT:

Here's the page you need:

http://support.amd.com/us/gpudownloa...w_vista32.aspx

Download the Catalyst Software Suite and install. Optionally, you can also download the Application Profiles, also available on the same page.

Okay, so now I am thinking that perhaps Bootcamp is to blame here. You did use Bootcamp to install Windows 7, right?

If you have a 2007+ iMac try this and see if it works: Apple Boot Camp XP Software Graphics Drivers