Time Capsule Backup/NAS Question

Hi, I hope someone can give me some advice on a few subjects. I am a long time windows user but have just purchased a MBP 13inch to see how I get along with it. Anyhow I am cognizant of the need to back up having previously had a PC hard drive die and loose some photos etc. I don't actually keep much on my mac hard drive really and currently have an old windows 7 PC that is slow but with a big hard drive for duplicating photos and music to as a back up device as well as two separate WD Hard drives - one of which is a MyBook Live NAS.

Unfortunately at some point the MyBook NAS has been damaged and I don't think I can write to it, although I haven't tried this with the Mac, but I can still read files on there. The main purpose of the NAS really is to provide a music storage solution for my Sonos system (and which still works happily for this purpose).

The first question is, if I can still write to the NAS drive, can I partition part of the disk and format that partition to be suitable for a time machine back up of both my MBP and my daughters MB Air (I really need to back her mac up more than mine as she has loads of stuff on it and she is off to Australia shortly and bound to loose the MBA somewhere in the middle of Oz if I know my daughter). If so, any suggestions how to go about this without loosing all of the existing data on the NAS - it has tons of spare space for this purpose.

Secondly, if the NAS doesn't work and I can't write anything else to it, should I buy a time capsule and use this for backups? - can I then create a separate partition on it for using as a music server to my Sonos system or is this something it is not designed to do? If this is the case I might be better off buying another WD NAS device to replace the current one (as I know how to work with this ok) however if anyone has any suggestions for an alternative I would be interested as the WD does seem a bit slow connected to a BT Home Hub 4.00

Next topic - can anyone point me in the direction of a tutorial on what Keychain does and how to use it. Having been a windows user since 3.1 I keep trying to think in terms of how the mac does things compared to windows and this probably isn't the right approach.

Lastly (for now anyway) how can I change autofill settings - everytime I want to fill an email field in on a web page the mac wants to complete either my dad's email address (and he doesn't have a mac) or my daughters and it is driving me potty!

Sorry for such a long post. I have been reading these forums since I got the mac and am constantly amazed that there are so many people willing to help mac novices like me, for which I am very grateful, so thank you in advance to anyone willing to read my post and take the time to respond

If I am understanding question one correctly there is no need to partition the drive in the typical sense of the word. Time Machine doesn't behave quite that way on a NAS. When Time Machine backups are stored on a NAS the backup is tired in what is essentially an expandable disk image called a sparsebundle. Each Mac would have its own sparsebundle file.

Thanks Slydude that does answer my question. Now I just need to work out if my NAS drive does work properly so I can write backups to it. If it doesn't it probably makes sense to purchase another one as they are cheaper than a time capsule and does what I need by the sound of things. Thank you for your help

You're welcome. I have one of the earlier Time Capsules and it has been rock solid but you're right. There are other devices out there that are reliable. I personally haven't even in the market for one in quite some time so perhaps others will have some ideas.