I've had never any problems with upgrades and never lost any files.
You should make a backup — or better, make a bootable clone of your current hard drive:
- Buy an external hard drive
- Install Snow Leopard on the external drive.
- Reboot into the clean external Snow Leopard drive, migrate over users and apps and run all updates. Run from that external to be sure it's a workable copy of your internal drive.
- Disconnect the external drive and put it on the shelf.
- Reboot back into your regular internal hard drive and proceed with the upgrade to Lion.
- Download Lion and run the installer!
Until you're certain that Lion works perfectly, keep the clone around - several months is usually enough time. If you ever need any files from it, just attach the drive and drag-and-drop them. If something goes really horribly wrong, you can boot into the clone, and then clone it back to the internal drive (you'll lose any changes made since you installed Lion). This second drive is really valuable for when you discover three months down the road that one seldom used piece of software won't work on Lion. You can reboot into Snow Leopard where everything still works and get that one task done. It's a great lifesaver and means you can start using Lion rather than checking that every little thing works perfectly right after the upgrade.
EDIT:
Thanks Trombone for editing my broken-english post, but please, never add your own ideas into my post. My solution uses pure apple tools, so why bother with SuperDuper, when you can do it with nice clean install and Migration Assistant.
I never recommend any third-party products when things can be done with default Apple SW. Of course, you can prefer SuperDuper, it is your way - but not mine. Please add another answer explaining how to use SuperDuper or other awesome tools so that people can have a choice. Let's keep this solution needing no additional tools.
Seeking clarification
Please add to the opening question a note of whether the panic occurs during:
a) the preparation stage of installation (before the first automated restart of the system)
or
b) post-preparation, the installation stage (between the first and second automated restarts).
Logging the preparation and installation stages of installation
Screenshots at http://www.wuala.com/grahamperrin/public/2011/08/01/a/?mode=gallery demonstrate the Installer Log window in foreground whilst Mac OS X Installer runs — the installation stage.
During either stage (preparation or installation) you can present a log window by keying:
With luck, you might see — possibly greyed-out beneath the foreground detail of the panic — the point at which panic occurs.
At the root of the volume to which installation is attempted: if installation fails you may find a directory:
Mac OS X Install Data
Within that directory, a log. If present, that log may be informative to you, but not as useful (to readers here) as the .panic file.
PRAM, kernel panic information and the .panic file
Apple's Mac OS X: What's stored in PRAM tells us that recent kernel panic information is stored in PRAM. If the first normal start following a panic does not present the customary dialogue, you should wonder whether/how that information was lost from PRAM.
If the kernel panic occurs during the installation stage — and if the subsequent start defaults to attempt continuation of the installation, or Mac OS X Utilities (not a normal start) — and if you are without an obvious interface to kernel panic information — then my hunch would be that whilst started in that special mode, the path to which a .panic file might normally be written is read-only …
… if that's the case and if you're comfortable at the command line, maybe start in single user mode following the panic then use the following command to see whether panic information is legible on screen:
nvram -p
(For the number of ifs above, apologies!)
Best Answer
When you turn on the computer, put the disc in the drive with one hand, and hold down the option key with the other. This forces the Mac to look for ANY bootable media. If nothing comes up, the hard drive is blank (as you suspect), and the ROM drive can't read the disc you are putting in (or the ROM drive has failed). You can try creating a Mountain Lion USB key. Incidentally, what Mac are you putting this disc in? A Mac Book Pro, an iMac? What generation? What CPU is in it?