I am not a super technical person, but I have come to realize that most technical questions have already been asked at least 1000 times before. So when I wonder about how to do stuff, I turn to Google…
Question 1: Is there a file system that I can use for both mac and pc? (Short answer: Yes, it’s called FAT32, but it’s not very good for large drives.) If I had the need to go between Windows (NTFS) and Mac (HFS+, aka Mac OS Extended), I would probably create a small-ish third partition (FAT32) as a go-between. FAT32 can be read and written to by either OS. But if you don’t like that idea, here is another answer. Basically, you install MacFUSE and then NTFS-3G, which allows macs to read and write to Windows/NTFS drives.
Question 2: Can I make a Time Machine backup bootable? Answer: Yes – sort of. I can copy my OS X Restore DVD directly to the Time Machine partition to be able to boot directly to the external drive and restore files without my mac. It’s not the same as a clone of my system because I can’t boot directly into my backup drive and continue working. But at least it keeps me from having to fumble around for my OS X Leopard DVD if I need to restore something directly from the backup drive. Here are the instructions.
If it’s important to be able to boot directly from your backup, a nice complement to Time Machine is some cloning software called SuperDuper! It not only allows an entire system to be cloned, but you can also boot directly to the cloned copy from any other mac (Intel or PowerPC). This means you could work uninterrupted from another machine while yours is being fixed. You have to buy the full version to get the backup scheduling feature, otherwise you have to keep your backups up-to-date manually. Here’s a little more about it. I don’t usually buy utility-type software, but at about $28 this one is tempting. (Even the free version is very nice for easy cloning. From my experience it works much better than Carbon Copy Cloner.)
Question 3: How do you make a Mac OS Extended (aka HFS+) partition bootable? This is important if you want to copy your Leopard DVD to a bootable Time Machine backup (see question #2). Run Disk Utility (in Applications –> Utilities folder) and select the desired partition. If Volume Format lists it as Mac OS Extended (Journaled) then it is already bootable. If not then click the “Enable Journaling” button. Presto! (This can be done anytime with a Mac OS Extended partition – even if you already have files on it.)