Historically, I've cautioned Windows users against upgrading from one version of the OS to another, because the result is often a crufty, Frankenstein-esque install that doesn't run as fast or reliably as a clean install. With Windows 7, however, I've been forced to reevaluate this advice.

In the process of documenting the various ways in which one can install and upgrade to Windows 7 for my latest book, Windows 7 Secrets, I've discovered that the upgrade process appears to work a lot more smoothly than it did in previous versions. Now, I'm not ready for a blanket reversal of my previous advice. But I've now upgraded a number of heavily-used and constantly updated Windows Vista- and XP-based PCs to Windows 7 (in additional to numerous, less relevant virtual machine installs). I've upgraded on desktops. On notebooks. On Tablet PCs. I've even upgraded a Macbook.

After evaluating these upgrades, my basic advice is still the same: Though they require more work, clean installs provide better results. But I do understand that many people, for whatever reason, prefer upgrading. This is true both of those that run older versions of Windows and of those who previously installed a Beta or Release Candidate (RC) version of Windows 7 and want to upgrade to the final version.