Vista - External HD recognized, but not showing- Help!

I have a HP Personal Media Drive. I transferred files onto it from a mac (OSX) (mostly .avi, audio and picture files). Many of these files were originally transferred onto the mac from another PC.

When I plug in the USB to the PC (HP G50 Notebook) it comes up as 'new hardware found' and 'installing driver software', and it always appears in the device manager. The device manager says that the driver is up to date and working properly. However, it does not show up under My Computer and I cannot open the drive to access any of the files. I have uninstalled and reinstalled it, with no difference. I plugged it in once again to the mac and the driver opened right up. Does it need to be formated or something? I don't know what I'm doing wrong. If anyone can help me out I would really appreciate it!

Thanks!

The partition type is the problem. For factory Fat32 volumes the installer for the drive's software has to configure it for Windows. If the drive is seeing a Unix type partition not Fat32 you may likely need to boot from a live Linux cd like ubuntu in order to copy files from it. Then you would simply see it reformatted to NTFS in the Disk Management tool in order to be assigned a logical drive letter for Windows use.