Time Machine feature?

Also, what format does the HDD have to be for Time Machine to be able to see it?

 

As long as the external drive has enough space for both computers, then yes. Say I have a MB and a MBP, with drives of 120Gb and 200Gb capacities respectively. I use half of the space on each drive, so if my time machine drive has a capacity of 200GB, it's perfectly fine, since 60 + 100 = 160, which in turn 160 < 200. I'm not sure if time machine will backup the windows partition, it should, as it backups the entire drive, not just the partitions.

The time machine backup drives must be in HFS+ Extended Journaled.

 

Doesn't back up your Windows partition but I'm pretty sure two Macs can use the same drive partition. If not, then the drive can be partitioned into two, and are treated as separate volumes.

To back up Windows files, create another partition (FAT32 this time) and just manually drag and drop.

 

Remember to identify "do not backup" directories

If you run any torrent software or peer to peer software or virtual machines, make sure you place those directories in the "do not backup" list on Time Machine.

If you do not put them in the list, TM will back them up every time it runs.

You will need to find a way to copy your virtual machines to a backup volume on a regular basis.