Which will be your primary system, Win or Mac? What's the size of hard drive? If you use FAT32 you gain compatibility but lose out on the benefits of NTFS or HFS+.
Better to choose any hard drive with a long warranty (3-5yrs not the 1yr joke) and format as HFS+ then use
MacDrive v7 to access from Windows side. Works flawlessly on my 2 WinXP and 2 MacOS network with 3 external drives.