media player

I hope someone can help me with this. I will admit i am a complete computer
'numpty' but I normally dont have problems playing videos,etc on media player
but have got a new laptop with vista and everytime I try to watch anything i
get this message
###Windows Media Player cannot play the file. The Player might not support
the file type or might not support the codec that was used to compress the
file.###
I have no idea what this means, it also constantly tells me I am not
connected to the internet when I am!! Have exactly the same problem with real
player so it is obviously something on my laptop that is stopping them
working but I dont know how to sort it out..HELP!!!!!