TimeMachine, Clonezilla, Mac OSX, Windows XP, and NAS

Hi all! I have no idea if this is in the right forum or not, so I apologize in advance if it is.

I'm looking for a network enabled/attached (via Ethernet CAT 5/6) external hard drive that I can use to
a)backup all machines (1 MacBook Pro and 3 Windows XP) using both Time Machine and Clonezilla (or equiv), and
b)serve media to all computers.

I don't need another router (meaning the Time Capsule), just something I can attach to my existing one. I've looked, and found either the Western Digital MyBook World Ed. 1TB or the OKGEAR LAN-SI 3.5” with a 1TB HDD put in.

I have two questions. The first is, has anyone used either of the two options above to do anything similar to what I'm trying to accomplish, and second, is this even possible? I'd like to backup monthly using disk imaging, with incremental backups occurring weekly.

I'm not sure if I've clearly explained what I'd like to do or how, so if you have questions, I'm happy to answer them.

If you have any ideas about how I could do this, I'd greatly appreciate it!

Thanks,
Jeremy