I've got NFS MW Black Edition running on both WinXP and Win7 and I've already got a report.
Under XP, it runs perfectly at 1024x768 with everything at maximum. However, in Windows 7, using the default video driver, it barely reached 30fps at 640x480 with all settings maxed out. So i downloaded and installed the latest official nVidia driver, and though the performance raised a bit, the difference to XP's is huge. I guess it's because this is an old game, optimised for DX 9.0c. Here are my machine specs:
Intel Pentium Dual Core E2200 @2.2Ghz
Intel D945GCCR MoBo
2GB DDR2 800Mhz Kingston
nVidia GeForce 7300GT PCIe 512MB
On the other hand, I tried Street Fighter IV on both OS, and I got very similar performance figures for both (slightly higher on XP). So this reinforce my theory that NFS MW has troubles running under Win7 because of its age.
Hope this info proves useful
Oh, BTW, I'm using RC Build 7100