You can do a couple of things to make it work.
1. Partition & format the entire drive on the Mac as HFS. Then purchase and install
MacDrive 5 on the PC. This will let the PC read/write HFS disks.
2. Partition & format the entire drive on the PC as NTFS (assuming you are using 2000/XP). Panther on the Mac will read NTFS partitions, but can't write to them. There is an open source project for Linux that supports reading/writing to NTFS partitions. I have seen people say they have compiled this on their Macs.
3. Partition the drive into separate partitions of FAT32/NTFS/HFS as you need. The partitioning is best done on the PC if you are planning to have more than 4 partitions. I read a thread somewhere from a person that partitioned their drive on the Mac with 8 partitions and then couldn't read it with their PC.