Intel X3100 Vista vs. XP Drivers

On the exact same hardware, I get approx. 600 3dmark06's on Vista and 300 3dmark06's on XP on the Intel X3100 chipset. I am using the latest drivers on both tests and identical driver settings post-install.

The update dates of both drives are within one month of each other, so on the surface, it would appear that Intel is keeping both drivers current. However I am beginning to think that Intel is intentionally retarding its GMA performance on XP (they're obviously very much in bed with Microsoft re: Vista - see, for instance, the "Vista Capable" lawsuit that details how Microsoft down-graded its Vista capable specs so Intel could sell its older chipsets for a little while longer).

I find Vista to be an insufferable OS (Windows 7 is much better - alas I cannot speak about it since we're under NDA with Microsoft), therefore its very frustrating that the 3dmark06 performance I get on XP is half of that I get on Vista. Crysis Warhead/Wars is playable on the latter (DX9 mode, of course) on minimum settings and resolution, but not the former.

I was wondering if anybody had any insights on this issue? What I'm specifically asking for is if anybody else can confirm my findings and whether they are able to get the XP performance on par with Vista performance. No other graphics card performs poorer on XP than on Vista, and definitely not within this order of magnitude, so I'm really wondering if this is Intel's "thank-you" to Microsoft for the whole Vista Capable shindig.