I am just about to install Snow Leopard. My question is if I will loose all my data if I INSTALL (not UPGRADE) the Snow Leopard OVER the Leopard?
I repeat: I do not plan to UPGRADE with the official UPGRADE pack, I'd rather INSTALL the Snow Leopard over the Leopard, but I do not know if all my data will be lost or saved?
Installing Snow Leopard "over" Leopard IS an "upgrade." Your existing user account data and settings will be retained. However, there is always a possibility that something bad will happen during a major system installation, so you need to have a backup of at least your personal data.
The only other option is to erase your internal drive first, then install Snow Leopard on a blank volume. After installation is done and the system restarts from the new installation, restore your personal data from your backup. This option will obviously erase your existing data on the drive.
In your place, I would move to SL if, and only if, I had an external drive with a bootable clone of my internal on it and had my files backed up in some other secure place. I think that there is enough risk in going to SL that such conservatism is warranted. I would not use time machine alone for backup/restoring. This app can be problematic and, consequently, its solo use is too risky for me. You will be able to extract your settings, files, and programs from your clone if you do an erase and install.
To erase and install, start up to your DVD and stop after selecting your language. Use the menus to start Disk Utility and erase your drive. Quit Disk Utility and proceed with your installation. At the end, you will be able to choose to reclaim your settings, files, and apps from the clone (plug in the external at the point of the last install restart).
If you do not like SL, then you can restore your internal using the clone. I would do all cloning and related restoration with SuperDuper or some other up-to-date cloning app. Your clone also will serve as an independent backup for your data.
Upgrading is a very sound process on a Mac. Still, I also would insist on having a bootable clone on an external before upgrading. An upgrade is performed by installing over your existing installation from the desktop or having started from your SL DVD. All you programs, data, and settings will be present after an upgrade, but incompatible programs will be archived.
