What color space does MSPaint use? (I believe all MSPaints are same for last several versions, but it just to make sure, I am Windows 7).
It would appear that it is HSL, however, the Lum goes from 0 to 240, but from what I read, on HSL Lum should go 0-100.
I assume you mean the model used in the Color dialog box in Paint. It's indeed the HSL color model, see:
http://msdn.microsoft.com/en-us/library/windows/desktop/ms646375%28v=vs.85%29.aspx
As I recall, this particular dialog box was used since about Windows 3.1. (Saturation and luminosity are actually on a scale from 0 to 1, here it's stretched from 0 to 240. Hue is actually on a scale from 0 to 360 degrees, here it's compressed from 0 to 240.)