you haven't given us much to work with. we really need the computer's operating system and service pack, which computer model, which pp and its o/s.
that having been said, i ran into a similar problem. i acquired a new dell laptop with no serial ports. i did find an adapter that would allow the 2 to connect, but needed software to tell the computer that the USB port was supposed to emulate a serial port.
i got the software and was able to synch, but it messed up my o/s (WinXP w/ SP3). i managed to figure out the problem (with a little help from my friends at dell) but was then forced to realise that i had to shelve my trusty pp in favour of an ipod touch. even then i am having challenges with it.
unfotunately, the only company making new non-phone item like the pp is apple with the touch.
good luck
per ardua ad astra