Maybe try downloading 'Mpc Editor' by midicase.
It's a free program and it should help.
It creates programs on the floppy disk that the Mpc will recognize
http://www.midicase.com/mpceditor/The whole transferring sounds of the computer to Mpc can be a bit tricky, I'm sure some of the more experienced heads on here have had better luck than me.
But that's the only way I've done it.
I generally find it's easier to just sample the sounds into the Mpc.
Then save them to Floppy disk.
To do that you need to format the floppy disk in the mpc
Shift -disk format - do it.
Hope you manage to get there in the end.
May the force be with you

Oh just noticed this was posted in 2008
Dude probably set fire to it by now.