As far as I know, a PATCH is only a set of parameters that tell the synth how to behave when playing sounds (which internal waveforms, envelopes, filter settings, etc), but the sounds itself (the raw waveforms used by the patch) are not included as part of the patch. This PATCH storage principle is common to all synths. Sound storage is another story and I'm afraid that the XP50 is not able to store its sounds on diskette. Therefore a XP50-written diskette has no meaning to an K2000VP.
However, if you want to play 'that XP50 lovely sound' on your K2000VP here is a solution:
If you have a PC with sound card, you can use it to sample the sounds of your XP50 to the PC hard drive. Then you can use 'awave', a popular shareware audio and instrument file converter to create Kurzweil files from WAV files, store them on the PC diskette and load them on your K2000VP.
If the K2000VP is able to sample from line-in, your last chance is to plug the XP50 main out to the K2000VP line in; sample, edit and save on the K2000VP drive.
I hope this can help.