Mouse acceleration always on, please halp

I moved to new apartment last weekend, and when setting computer up, I suddenly had mouseacceleration on(didn't had it 1 day before at old place)

1. I didn't remember which usb port my mouse was plugged, so I just did try&error method finding the one port which was overclocked to 500hz.
2. When mouse was plugged in(mx 518), it had acceleration. Inside Windows (win 7 64bit) and in games.
3. Ran markc fix, no effect. Modified reg values manually(for markc fix values and also tried win xp values) to make sure it takes effect, didn't help(yes, booted computer afterwards). Mousemovement recorded said everything was fine.

What to do?

Edit: Didn't touch to any settings, acceleration just came to stay, windows reinstall incoming unless someone finds a way to fix this.

Edit 2: Fixed it by switching mouse to another usb port(usb 3.0) which was also clocked to 500hz(and I think I had my mouse at this port before). Dunno why it behaved as it did in another port o.O