Few PC Magazine staffers advocate installing a new as directly over an exist¬ing as. A clean install, where you wipe the hard disk out first, is almost always preferable. Your new as will perform better, but you may wipe out some set¬tings-and you'll have to reinstall all your applications.

Oliver Rist, our PC Mag Labs networking analyst, says Vista is "a clean¬wipe upgrade only," especially when the upgrade is from XP. "Microsoft and upgrades just don't go together," he says. "There's no reason Microsoft couldn't do much, much better in this department. As a clean install, however, Vista is notice¬ably easier than any previous Windows version, including XP."

A clean install of XP could take an hour, but Vista is faster, even though it takes up more disk space. Vista is also better at handling system resources, such as giving back RAM it's not using-but you need high-level hardware to get the most out of it.
Ubuntu installs have a mixed track record with our staff. Associate editor Jennifer DeLeo's update from 7.04 (Feisty Fawn) to the current 7.10 lost sound, con¬nectivity to the Internet, and more-and this was on a Dell computer that came with 7.04 preinstalled. But others have encountered no problems.

Contributing editor Edward Mendel¬son believes that planning ahead is key for an Ubuntu upgrade. "Create a sepa¬rate hard disk partition for your /home directory for your data and applications. When it's time to upgrade, you can wipe out the system partition and install a new one, and your /home directory will still be there." Ed also advocates using Ubuntu LiveCDs, which let you run Ubuntu from a bootable CD-ROM without installing it to the hard drive. They're a great way to access an unbootable Windows PC so you can recover all the data. And they're a great way to give Ubuntu a free try, no strings attached, if only to see whether it recognizes your hardware. Rest assured ifit runs okay from a LiveCD, it's going to be fine from the hard drive.

Ubuntu can create a dual-boot instal¬lation with Windows on your hard disk. It even handles the disk partitioning for you. And it doesn't take a lot of time to install, either-usually under half an hour. Just don't try to mess with the partitions afterward. One staffer (okay, me, Eric Griffith) did that with Partition Magic and found himself with a system that wouldn't boot XP or Ubuntu. A clean installation of XP and then another of Ubuntu cleared up my laptop problems, however.

The clean-install exception is the Mac OS. Most users don't have to wipe out Tiger to upgrade to Leopard. Apple provides an "archive and install" feature in which apps and data stay the same, but your system software is brand new. Despite whatever other potential shortcomings Leopard may have, the installa¬tion is a breeze.