Windows 7 - Big loss of FPS after Seven migration

Hello
I've just migrated my old PC to Windows 7-Pro-SP1, and now: 3DMark2001SE score is 12000pts.
I had 17000pts when running WinXP-Pro-SP3.
Of course, I ran before migration, the "Microsoft Windows 7 migration advisor" and it just told me all will be fine.
All the windows update did run OK.
I've tried to replace the video-driver with the last nVidia, score is lower: 11000pts.
Of course, no anti-virus during the test; and task-manager is calm.
So I think I encounter a problem, but where to search ??
Conf:
=====
P4 3.2GHz HT
2500MB DDR1 in dual-channel
video AGP 8x 7600GT
HDD 500GB SATA1
all hardware exactly the same as under WinXP

Thanks in advance,
$martiz

New try: I've disabled Hyper-Threading, and score is the same
Other test: in BIOS setting "AGP aperture size", was 256MB, tried with 64MB, exactly the same.
I am sure there is one "big" reason to low score 17000pts to 11000pts, this test http://www.firingsquad.com/hardware/windows_7_gaming/shows that performance are quite identical with WinXP !

The video card driver is not optimized anymore for such and old application, try a newer version of 3DMark, or go back to XP?

You're right, probably no more optimized for DirectX 8 ...
I also notice severe lost of graphical ressources in OpenGL game (Ennemy Territory, a Quake3 engine-based), just 25 fps in maps where having 70 and more on XP
So thanks for smart advice "go back to XP"
Bye all