Some consumers who upgraded PCs to Windows 10 are reporting unforeseen software compatibility problems.

Christopher Restemayer of Menahga, Minn., pointed out that many upgraded PCs can't locate their DVD-CD drives because Windows 10 lacks the correct software drivers for them. I originally wrote that Windows 10's lack of DVD playing software was the cause. But Restemayer's idea is backed up by several online forums. Consumers have three choices:

• Go to the website of the CD-DVD drive manufacturer to look for a downloadable Windows 10 driver. Normally, you'd find the manufacturer's name by typing "device manager" in the search bar, clicking enter, then clicking the triangle next to "DVD/CD-ROM drives," but it's probably not there in this case. So search online for your PC's specifications.

• Alter the PC's registry. This is risky and the average consumer shouldn't attempt it. For the technically inclined, see tinyurl.com/p3vhu7x or tinyurl.com/odhhtkp.

• Reverse the Windows 10 upgrade to Windows 7 or Windows 8.1. See tinyurl.com/nqqgl8p.

Becky Wofford of Eldorado, Texas, says her HP LaserJet Pro wireless printer doesn't work well with Windows 10, and wonders if she'll have similar problems if she returns to Windows 7.

She most likely needs a Windows 10 compatible software driver for either her printer or her wireless network. Check out HP's Windows 10 help page (tinyurl.com/peejx72), which deals with software drivers, Wi-Fi and Bluetooth wireless connections, PC start-up and shutdown, and speakers and microphones. If the printer worked with Windows 7 before, it should again. If it doesn't, download the Windows 7 printer driver at tinyurl.com/qayn6kr.

Susan Thayer of Eagan couldn't access her Yahoo calendar after upgrading to Windows 10.

To establish or improve the connections between Windows 10 and your calendar and e-mail accounts, see tinyurl.com/q4qkkmr.

Jan Schieffert of Bloomington said that, after reversing the Windows 10 upgrade to Windows 8.1, she could no longer use the HP PC's touch-screen controls when in tablet computer mode.

It seems that the PC has lost the Windows 8.1 software drivers for the touch screen. Those drivers can be restored with the PC's original Windows 8.1 recovery disks (back up your data first). If you don't have the disks, order them from HP at tinyurl.com/nlr6r68.

Sharon Turner of Atascadero, Calif., says her PC frequently prompts her to install Windows 10, which she doesn't plan to do. She wonders if the upgrade could happen automatically.

No, an upgrade will happen only if the user agrees to it. To get rid of the prompt, go to Control Panel, then System and Security, then Windows Update. For details, see tinyurl.com/o9k9hno.

E-mail tech questions to steve.j.alexander@gmail.com or write to Tech Q&A, 650 3rd Av. S., Suite 1300, ­Minneapolis, MN 55488. Include name, city and telephone number.