Time Machine Questions...

Time Machine works only with Leopard, if you are talking about Time Capsule (the wireless backup from Apple) then it will work with other machines on your network.
Time Capsule backs up on an hourly basis files on your Leopard OS via Time Machine (the backup utility).
If you have a mixed environment such as Mac OS X Tiger, Vista or XP machines then you can still use Time Capsule but not for backup, you can only use Time Capsule as a network attached storage so you can drag and drop files to it from any of the above OS's.

If you already have an Airport Extreme base station you can buy a Drobo, Western Digital or any USB external drive if you just need network attached storage. If you need a wireless router and an external drive Time Capsule will be good solution.

 

You'll need more than 120 GB if you want to keep a history of files you deleted. I'd recommend at least 200 GB. More is better.

Yes, you can. However, TM will eventually fill up your harddisk with old backups and you will have to delete backups manually to make room for other data. Furthermore, TM needs HFS+ while data exchange with Windows machines needs FAT32.

You could create two partitions on the disk but I don't know how compatible that is with other systems.

It's easier to simply buy two smaller drives. This way you'll not be carrying you valuable backup data around.

 

Buy a big ass drive, and use Drive Utility to partition it, leave Time Machine to have its own partition (although it does just create a folder on the drive which it stores its bits in), and use the other for transfer.

 

You'll need a separate drive for Mac and Windows. It's just easier in the long run to keep them separate. For the Mac drive, no partitions are necessary. Just let TM start backing up and then you can copy other files to it as needed. TM will use only the space it needs and the rest will be available to you. All the backups are in their own folder so why partition off valuable disk space that you can use now?

 

Something for you to consider when creating a backup system.

If you partition a drive and use part of it for backups (Time Machine or any other product) and then use the rest of it for data storage, herein lies the catch. Do you want to backup that data storage area to your backup system? If you do, and use the method above, what happens if the disk that holds the backup system and the data storage fails? You lose both, in short order.

So I would recommend that you have a single external disk for backups, and if you need data storage space other than your internal disk, then get another external. Then add that to your backup schema. Now the chances of you losing data goes way down unless we take into consideration an unfortunate lightning strike or something on that order.

My two cents worth...