My Laptop is Dell Inspiron 15R, Running Win 7. Sometime I am Getting Some Error Like Its Getting Restored Size Of Media Player When I was in Full screen Mode of Media Player.

Do Anyone Help Me Please ?

Don't run Media Player. Download and install VLC - trust me, you will be a LOT happier!

FWIW, the only thing that VLC can't run that MP will, are encrypted videos.

Could be some background programs forced Media Player to restore from full screen. It seems to be a glitch from Media Player itself anyway...

You can try other media player for instance. VLC like Rubberman suggested. I would suggest Media Player Classic though... It bundles with codecs so you can run almost any video on Windows Media Player...

not only does the SOMETIMES error not make much sense to me , giving the links in OP's signature i don't think they will be back anytime soon