Q: I converted my Windows 7 PC to Windows 10 in 2016, when Microsoft was offering the upgrade for free. But I didn't like Windows 10, so I chose to undo the upgrade. Now that Windows 7 no longer gets security updates, I want to install Windows 10 again. An IT guy told me I might still be able to get it for free, even though the free upgrade offer has expired. Can I?

Gary Lovell, Toledo, Ohio

A: Yes, you can still get the free upgrade to Windows 10, even though the Microsoft offer expired in 2017. The download and installation process remains available for all Windows 7 or 8.1 PCs that can handle Windows 10 (see installation directions at tinyurl.com/yxyczvnx).

This unpublicized giveaway is unusual for Microsoft, and comes at a time when there are still plenty of PCs that need to be upgraded (see tinyurl.com/y94nuduj). About 25% of personal computers still use Windows 7 (even though it no longer gets security updates) and about 3% use Windows 8.1 (which gets security updates until January 2023).

So why has this freebie continued? I suspect that Microsoft is more interested in getting rid of older, less-secure versions of Windows than in making a few extra bucks selling Windows 10 upgrades. Windows 7 PCs, for example, appear to be a hacking disaster waiting to happen.

So, here's how to upgrade to Windows 10 for free:

• Download Windows 10 via Microsoft's Media Creation Tool, which creates an installation program on a DVD disk or flash drive (see tinyurl.com/hgtcedm and click "download tool now.")

• Get your Windows 7 or 8.1 PC ready for the upgrade. Download the newest available software drivers for your PC. Disconnect any external devices from the PC, including disk drives, flash drives and printers. Uninstall your antivirus software (you should reinstall it once Windows 10 is installed.)

• Install Windows 10. When you are asked what you want to keep on the PC, be sure to choose "keep personal files and apps." If you choose any other option, Windows 10 may not install.

• Activate Windows 10. The upgrade will automatically convert your Windows 7 or 8.1 digital license to a Windows 10 license. To activate the Windows 10 license, go to Settings and choose "update & security." Then click "activation."

Gmail issues

Andrea Nikolai of Lakeland, Fla., says she can't receive e-mails in her Gmail account.

A: You have probably exceeded the 15-gigabyte storage limit for a Google account, which means you need to delete something from Gmail (e-mail and attachments, some of which can be large files), Google Photos (photos only, typically large files) and Google Drive (stores any kind of data.) Note that only Google Photos files can be compressed to take up less space; convert them from original quality to high quality (see tinyurl.com/yxkmmlvh).

Anita Winkley of Winter Haven, Fla., said she's losing e-mails and their attached photos from Gmail, and wonders if e-mail filtering is set up incorrectly.

A: Gmail's filters can be set up to block e-mail based on the sender, subject line, wording, size or attachments — or a combination of those things. If the filters are deleting e-mail you want to keep, you should erase all e-mail filters and start over (see tinyurl.com/n3ujj7f).

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