MPC-HC settings not saving?

[telephony]

It seems my settings aren't saving for some reason, or it reverts back to some default, like randomly starts with D3D Fullscreen.

Where are MPC-HC's settings file located or how do I make sure my settings are saved?

[Hypernova]

Where did you install it and did you use .ini? I think if you're not using .ini then MPC-HC will try to use registry, and with Vista/7 that could means admin privilege needed.

[namaiki]

Also it's possible that you might accidentally enable D3D Fullscreen as the keyboard shortcut to toggle it is (or at least it used to be) Ctrl+F.