Should I boot from external hard disk and how do I achieve this?

I'm in a downward spiral and need advice about if booting off of an external hard disc is the right thing to do and how to go about it. How I got into this mess I'll write below. My immediate problem is that I want to be able to install a copy of osx 10.5 from the original disks that came with my computer onto a usb hard drive. Then I want to boot from that drive and install software such as disk warrior on the same external hard drive in order to repair and recover the files on my internal hard disk. Not sure if this is easy to do with the install disk that came boxed with my macbook. So is what I want to do feasible and how do I do it? Thanks.

How did I get into this mess?

For those with time to read more. A downward spiral (and my macbook was working fine)::

I have been backing up my work documents onto a 20 GB pendrive waiting to get the money to buy an nas to work with time machine for the two macbooks we have at home as a place to backup photos and video. I bought a network drive but it wouldn't work with my macbook; my time machine backup freezing at 3 gb, but works fine with wife's macbook pro.

I tried to do TM backup on a usb hard disk and got the same problem. Support forums indicated that hard disk problems could confuse TM, so although I was experiencing problem free computing I ran disk utility from internal osx. This indicated an <invalid node structure - file system verify or repair failed> at the checking catalog file stage. So I followed instructions to run disk utility and repair from the installation disk. When I ran disk utility from installation disk I get exactly the same <invalid node structure - file system verify or repair failed>. It gets worse.

After failing with install disk utility, I could not then boot from my hard disk (I had had trouble free computing up to my attempts to use TM) or eject the disk. At first attempt I had no option but to boot from dvd again as hd not offered as an option. Second attempt hd option available but fails. By reading advice given to others I managed to eject the dvd and have tried:

• safe boot - it won't
• boot in verbose mode and single user (indicates I have disk0s2:I/O error) and won't boot
• try to use disk utility from install disk to create disk image on external hd, it won't (cites i/o error)

If I can boot from an external I will try to repair with Disk Warrior as forums indicate that this software has been able to solve <invalid node structure> issues (but am open to recommendations of other products). I also hope that I may be able to try again to burn a disk image sucessfully if this repair works. I'm still trying to save my photos and videos that aren't backed up.

I plan to try an archive and install installation but first I want to try a repair with disk warrior as I fear that archive and install won't work and I'll end up having to erase and repair my hard disk.

I feel like some perverse god is punishing me for trying to do the right thing and back up my hard disk.😟

Macbook 5.1 late 2008

Intel Core 2 Duo

OSX Leopard 10.5.8

85 GB of a 150GB hard disk needs backing up (saving)