Mail Problems, Update

Hi guys,
I've been looking around the net, I know there have been a lot of problems like this but mine is different and slightly more complex.

I didn't install, or possibly removed the mail app when reinstalling the os (10.5) to use a different program. But for various reasons I want to switch back. The only issue is that I have updated to 10.5.8 with the combo update. Which renders the mail app from my os disc unable to open (you cannot use this version of the application mail with this version of the os).

I downloaded both the 10.5.8 update and combo update to try to extract the mail app with pacifist, but the file i was told would have it (called archive or something) isn't there. I extracted the mail app as it was but it doesn't open. Software update and appfresh don't recongnise that it is there to be updated either.

So i really have 2 questions.

Is it possible to download mail from somewhere?
Or can i just repeat the 10.5.8 update which I have downloaded?
Is it safe to do when I already have it installed?

One more thing, my backup hard drive is faulty, and until a replacement arrives I am without a backup, I have one I can use if I have to, but if i can hold if I would prefer it.

Thanks in advance

What year model Mac do you have? If you have an Intel Mac, it may be easier to upgrade to Snow Leopard for $29 rather than trying to get Mail to install.

Nice idea, thanks, i hadn't thought of that. I think that might be what i do.

That one will have to wait until i've backed up though, i think. Or can I start a time machine back up on an external hard drive which has data already on it without losing the data?

Is there also any software that will automatically back up one external hard drive onto another?

Time Machine will not overwrite any data that is on the hard drive. However, be warned though... if the external drive is not formatted as HFS+, Time Machine will reformat the drive which will destroy all the data that is already on the drive.

Backing up from one hard drive to another is a matter of copying the data from one drive to the other.

Thanks for the info, you probably saved me a whole load of data and frustration.