I am not perfectly sure if I understood your question correctly, but anyway: In case you want to use an external HDD on both, PC and Mac, then this drive needs to be formatted in FAT32. Windows doesn’t support Apple file systems, and MacOS doesn’t support NTFS.
The main disadvantage of FAT32 is, that the file size is limited to 4 GiB. Also you need 3rd party tools to format a partition larger than 32 GiB in FAT32.
Yes… that’s the dilemma. I want to be able to store and retrieve files from both W7 and OSX on the external HDD. When you say Windows doesn’t support Apple file systems, does that mean you can’t dump a file created on the mac (say a home movie clip) onto the PC for whatever reason? And the other problem is most archived movie files are around 4 GiB +/- right? And IIRC, its either ATV or the Apple Airport that doesn’t recognize FAT32 drives, or am I confusing the issue? Then there’s HFS+… would it not be better to format the external HDD this way than with a windows format?
I had originally kicked around the idea of a two-drive Netgear or similar NAS drive, but some people don’t think you can stream video from one of those.