Sometimes you can't win for losin'.
Many Windows 7 and 8.1 users have put off upgrading to Windows 10 -- often for good reason. Some, though, have given in to the pressure, and they're trying to get the free upgrade in before Friday's deadline. And some of those folks are hitting a well-known problem: The upgrade installer stalls at 99 percent.
Faced with an impending deadline, many are loath to follow Microsoft's official instructions, delivered by Microsoft engineer and Answers Forum moderator Arvind Ram last week:
We are aware that a set of users are reporting a slow or seemingly-stuck upgrade experience when attempting to upgrade to Windows 10 or update between versions of Windows 10. The upgrade process usually takes 90 minutes or less to complete, but there is a very small subset of PCs, usually older or slower devices, where the upgrade process can take longer than typical. This situation is not related to a specific upgrade tool and has been shown to happen with Windows 10 Upgrade Assistant, Media Creation Tool, USB media, and ISO media.
In these cases, even if the progress percentage appears stuck, the upgrade is still running. An error message should be displayed in case of actual failure. Cancelling and trying alternate methods is unlikely to improve the experience and will reset any upgrade progress made.
We recommend the user wait until the upgrade completes before taking further action. Users can keep working as normal while the upgrade is in progress. A delay of one day would be highly unusual, but we recommend that users wait that long for the upgrade complete or to confirm there is an issue. At that time, users should reach out to Microsoft Support or visit a Microsoft Store location so we can look into issues with the PC.
You'll find a lot of advice all over the web, only some of which seems pertinent. I continue to recommend a series of simple steps:
If you live near a Microsoft Store, take your PC in and have them do the upgrade. If they can't get your Win 8.1 PC upgraded, they'll give you a new Dell Inspiron 15, free. If they can't get your Windows 7 PC upgraded, keep your receipt. That's ironclad proof that you tried to upgrade before the July 29 deadline.
If you don't live near a Microsoft Store, make sure you've disconnected any nonessential hardware: Unplug all hard drives other than the C: drive. Yank that external hard drive, disconnect peripherals that aren't absolutely necessary, including extra monitors, smart card readers, weird keyboards, whatever. If possible, consider turning off Wi-Fi and plugging into a router with a LAN cable (that worked for me). Then try running the upgrade again.
If that doesn't work, use the Windows 10 media creation tool to create a USB drive (or DVD). See the Download Windows 10 page for details. Be sure you follow the steps in order.
And if that doesn't work, get on the Microsoft Answers forum and complain -- loudly. Do it by Friday night. Your only recourse if you're really stuck is to phone in and request a Windows 10 activation key. It won't hurt if you can point to a series of unambiguous posts that say you tried to get installed before the deadline was up, but couldn't.