Indeed, there are three well-documented glitches that can strike Windows 7 upgrades: the installer hangs at 62 percent, the system reboots endlessly, and the dreaded "product key not valid" error.
PC World explains how to remedy all three glitches in Fix the Most Common Windows 7 Upgrade Problems. Here's an excerpt from the section on "hung" installations:
The culprit is a service called Iphlpsvc, which may stop responding to the system during the installation. Fortunately, the solution is relatively easy. If you don't feel like messing around with your system settings, download Microsoft's automated fix, MicrosoftFixit50319, and install it. Follow the wizard, and it should resolve the problem in about a minute.Good stuff. If you've been through a Windows 7 upgrade, how'd it go? Share your stories in the comments. And after that, check out these other handy Windows 7-related posts: