Is it possible to play .sid (Commodore 64) files in Media Player Classic? There are plugins for: WinAmp (SidAmp), XMPlay (xmp-sid) and some other players..
No, you can't play them in an emulator, they aren't in anykind of C64 format, if you want to play them in an emulator (or on a real C64) you must convert them first (with http://psid64.sourceforge.net for example), there are filters/plugins (and standalone players for sid) for many players, but I can't find one for MPC.