Original Prophet-5 and Prophet-10 patch bank data in sysex format can easily be imported directly into P-10 via drag-and-drop. These must be in "Syntech" .syx format.
IMPORTING SOUND BANKS AND INDIVIDUAL PATCHES USING A COMPUTER
To import an entire sound bank, simply drag and drop the bank anywhere over the P-10 UI.
If the bank is valid, you'll see a confirmation window and new category containing the banks is created in the presets browser.
IMPORTING INDIVIDUAL PATCHES FROM A PROPHET-5 OR PROPHET-10
This is admittedly a little dicier. Original Prophet-5's and Prophet-10's had a bug in their factory MIDI kit code that caused them to transmit "malformed" sysex. This means that transmitting a single patch to P-10 will not work, however there's a developer named Tauntek that has created updated OS's for the Prophet 5 and 10 that fix this glitch (these OS's also add some cool features). We haven't installed these in any of our Prophet-5's or 10's, but the ROM chips are available at the links below if this interests you:
http://www.tauntek.com/Prophet5.htm
http://www.tauntek.com/Prophet10.htm