Leopard killed my mini... HELP! :_(

Question

After many years of faithful service, I decided to give my mini (intel solo) a well deserved upgrade. I got Leopard from the Apple Store, installed, upgraded to the latest version (10.5.4), played with it throughout the weekend, and then, as I sat to watch a movie... it just sized up!
Frozen. Nothing will work. Oh well, nothing I hadn't seen before. Forced restart should sort it out.. Nope, frozen on the grey Apple screen... Lets have a look at Disk Repair from the DVD... Starts OK, runs OK, no repairs needed on the disk. Hmmm. Repair permissions... Nothing wrong there either, all permissions OK.
Restart Mini... same grey screen...
OK, so let's re-install Leopard, I've got plenty disk space...
Anyhow, after almost 3 hours, I decided to go to bed. It should finish overnight, after all, it says it has only 4 minutes left, even if it has said it for the last 30 min... give it time...
This morning, six hours later... still had 4 minutes to go. Installer FROZEN!
Now I don't have enough space left to re-install (only 2GB left).
So here come the questions:
1/ How can I set the Mini to Disk-Mode in order to free more space and/or copy some of my files? (I had pretty much everything backed up before I did the upgrade, but I was silly enough to but a few films from the iTunes shop; these weren't backed up...)
2/ I have two 500GB Iomega external firewire disks, so I thought I should be able to install Leopard in one of these and then access the mini's HD... The installer didn't allow me to do so, and asked to partition one as GIU-something... anyhow, as the two are identical (one is permanently mirrored into the other) I decided to erase one to install this new partition... but I couldn't find the option to install this particular kind of partition...
3/ If my mini ever goes back to life... should I go back to Tiger, keep to 10.5.0, or risk fate and go back to 10.5.4?
THANKS!

Answer 1

To answer your last question first, there are many people running Leopard quite happily on all varieties of Mac mini (and indeed far older systems) so there's nothing wrong with installing it again, and no reason to be reticent to do so if you like the features Leopard offers. It is worth saying however that if you were happy with Tiger, and liked the feature set of MacOS 10.4, Leopard doesn't really offer much in the way of enhancements, yet does typically require more RAM to run comfortably, particularly if you run multiple applications at the same time. If your Core Solo has 512Mb RAM and you run a lot of applications at once, or a number of old non-native software, you'd be better either increasing RAM to 1Gb or maxing out to 2, or returning to Tiger.
My guess is that when you installed Leopard, you performed the standard 'upgrade' install, and if so, that may well be the root cause of the problems you've had. This update path has created problems for many users, often the result of issues pre-existing on the system and which were largely hidden.
To back up the files on your mini before reinstalling, you can put it into Firewire target disk mode by holding 'T' down while booting while it is connected with a firewire cable to another Mac. That will mount it on the other Mac as an external drive and allow you to move files on and off it as with any other type of external.
What you then need to do is to reboot the mini with the installer (whether your existing Tiger or new Leopard installer is up to you) and then from the 'custom' install types, select 'Erase and Install'. This will wipe the internal drive of the mini and install a fresh copy of MacOS. That will resolve any outstanding drive/data issues, and give you a system that once completed, will be as it was when it came out of the box, including requiring the initial setup once again. Once that setup is complete, you can then reinstall your software and move your data back from the backups.