Ive got a replay and its a .mpr what could play it or do u ave to put it in ur lfs folder?

put it in the mpr folder of lfs, then open lfs and go to replays and multiplayer and watch it

If the replay is from a server in S1 or S2 mode, you can't watch it until you have bought S2 licence also it must from the version of LFS you have, otherwise it displays error "Obsolete video" OR seems to work but goes out of sync.