Unless it changed in the mean time, VAC bans by game engine.
So if you're banned on one game, you will be banned on any other game using the same engine.
I don't think any other game uses the same engine as MW2. Not sure tho.
But if you're banned in say TF2 you'll be banned from CS: S, DoD:S, HL2: DM etc as well.
Another reason why your unused MW2 might be banned is when someone already used your cd key. (If you bought a key online for example)