Best way to back up before applying 'risky' updates?

[Guest uklloydi]

I'm well used to carrying out backups on my various Macs, be that incremental Time Machine backups or full clones (using Carbon Copy Cloner).

I've got a certain distance with installing OSX on my MSI Wind (on 10.6.4) and want to apply the 10.5.5 and 10.5.6 updates. However, I'm aware that it could quite easily go tits up again, so I have taken a backup. I did a complete clone using Carbon Copy Cloner on to an external USB2 drive. CCC says that the drive will be bootable. However, it does not show int he Startup disks in OSX, nor can I pick that external drive from the boot menu (pressing F11 at startup).

I'm sure I'm not the only person here who wants to safeguard progress to date, so I'd like to know what the best way to do this is. Note that currently my MSI wind has no working Wifi and Ethernet is not working, so my only option is backing up to a connected USB drive right now.

Can anyone tell me what I should do?