Yeah the "Unknown Filesystem" was my mistake, it's been a while since I've looked at one. It's giving unallocated because winXP does not understand the file system on the drive.
If you repartition it to fat32, you will be able to read and write from both windows and mac OS. However please note, fat32 only allows individual files up to 4GB and does not allow for securities and permissions on the files.
You can also get software that will allows your windows to read the HFS+ filesystem at this link
http://www.mediafour.com/products/macdrive/ If you can live with the 4GB max file restriction, and do not use permissions, fat32 is the easiest and cheapest way to go.
Also note: You may have trouble copying the files back onto the drive after converting it to fat32. If you do it is because they have permission settings of some sort. In which case I would just change the drive back to HFS+ and purchase the program.
