Run the Upgrade Advisor to see whether your hardware configuration will support upgrading to Vista. You may need to beef up your machine for it to run Vista, or you may decide to ditch it and buy a new, more modern computer.
Back up everything. EVERYTHING.
Check for viruses on your system, then disconnect from the Internet and disable your antivirus software prior to upgrading.
Use Windows Easy Transfer to copy your user data and settings to your new machine (if you bought a new computer for running Vista).
Mitch Tulloch was lead author for the Windows Vista Resource Kit from Microsoft Press, which is the book for IT pros who want to deploy, maintain and support Windows Vista in mid- and large-sized network environments. Mitch was also the author of Introducing Windows Server 2008 and technical project lead for the Microsoft Office Communications Server 2007 Resource Kit, both books also from Microsoft Press. For more information on these and other books by Mitch, see www.mtit.com.