Mac Migration Assistant

The Mac's Migration Assistant, found at /Applications/Utilities/Migration Assistant, can transfer your software, settings and data from one Mac to another. You can actually transfer from another Mac, another volume on your Mac or from a Time Machine backup.

Mac OS X installation DVD

Following methods can be used to start your Mac from the Mac OS X install DVD:
1. Put in the DVD while your Mac is running, then select it as the startup destination
2. Turn on your Mac while holding the C key with the DVD inserted
3. Turn on your Mac while holding down the Option key while the DVD is inserted. It will fire up the Startup Manager.

With the Installation DVD, you can also reset password, set the firmware Password, check out your System Profiler and restore your entire system through a Time Machine backup.