Hi. I was hoping that I might find some help here.
It was time for a format, and I decided to nab Windows 7 this time around. Turns out, my games play worse, and I can't figure out why. Overall I've done four attempts to install Win7, with a reinstall of my XP Pro (32bit) somewhere inbetween that still performed better.
Games played by me are Team Fortress 2 and a little bit of WoW. The framerate in my games is just painfully much less in Win7 than it is on XP. The things making this hard to diagnose is the fact that my TF2 runs a nice 40-50fps on 24-player servers on max settings on the XP install but at about 10-20fps on Win7 any time there is action on the screen (although it still runs silky smooth when I'm in narrow corridors without much much going on). Minimum, maximum: there is no framerate difference no matter what I choose for video settings; the performance is actually the same. WoW of course has a painful degradation in framerate as well.
I've even tried both 64bit and 32bit installations; the 32bit actually runs a little worse, but they both still suck. Aero is disabled.
I noticed that the performance is pretty close to that of the XP installation (plus a little bit of hiccuping) when playing windowed TF2. Did not try windowed WoW, and it is not installed on the current Win7 installation.
Windows 7 Ultimate
Soltek SL-K890Pro motherboard
3 gigs of ddr1 ram (reads as 2.75 available, for some reason says 18gigs total), 2x identical 1gb + 2x identical 512mb sticks
AMD Athlon x2 4200+
GeForce 9600 GT
500gb Seagate Barracuda 7200.10
Well Windows 7 is a bit more demanding than Win Xp and I notice you're using DDR1 ram and you have a bit weak dual core. Your GPU is fine and it runs DX10 but if I had it my way I'll stay with Win Xp to enjoy great performance.
7 is more demanding on older hardware, but I wouldn't expect it to halve your framerates.
You mention that changing video settings makes no difference to performance; this points to a likely CPU bottleneck.
Have a quick look at your power settings. When I first installed Win7 it set my power profile to Power Saving for some strange reason. This prevented my CPU from going to full speed, with the result that everything ran slowly.