Yes, lots of other companies do really basic USB soundcards: Edirol, M-Audio, Griffin, Belkin (I think)..... some are pretty much just stereo inputs on a little block one end & a USB plug on the other. You can then record straight from your MPC on the computer.
If you just want to get your samples & sequences into the computer on a floppy I guess just see if the PC will read an MPC floppy. I've just stuck an MPC floppy in a real old-school Mac Performa (12 years old now) & that read .wav, .snd, .pgm & midi files........it can't do anything with them apart from store them but it is worth knowing!!!
If that doesn't work see if you can save to a PC formatted floppy in your MPC.