How to change gamma in fullscreen ?

[noxiousnic]

Salutations all, and apologies if this is documented somewhere else.

I use the DL 4.0 version of SpMBT, and find myself playing in a 800x600 window rather than fullscreen because under my monitor/vidcard setup, it's too dark and I can't tweak the gamma, or brightness/contrast/saturation in full screen mode in spMBT, one of the only games to exhibit that behavior : normally, a game running in fullscreen DirectX can be configured through overlay controls, if the regular color correction doesn't work.
I can correct the brightness and gamma fine in windowed mode, be it GDI or DX.

Any tips, insights welcome to workaround this problem.
Incidentally, does the full version use different rendering code, or it's the same but with more resolutions ?

Btw, this is an ancient PC, with a GeForce1 card and an old Sony monitor...
Yes, I can somewhat tweak it with the actual monitor brightness button, but it's not satisfactory in this particular case

Thanks in advance,
Cheers,
N.