Hi !
If I consider the Player is working perfectly and only problem is PC did not recognizes the player then...
This problem is not due to the player.
It is the problem of either USB port of your PC or USB cable.
If it is only MP3 Player, you can check with other USB port (I want to mean onboard USB Port) directly without using cable. If it is MP4 Player then you can check the same with another cable.
Clean the male and female part of cable, and Player using cleaner.
Also check the USB port cable connection with motherboard in case of front USB ports.
ii) Reinstall the USB mass storage drivers from motherboard manufacturers Driver CD (in case of original Intel board use ExpressInstaller CD)
iii) Some preliminary version of WIN-XP may not support these player, in that case it is better to try with XP-SP2.
iv) In case you need the USB driver for your player check the link www.s1mp3.org
Regards
skyshopindia