Q: I haven't been able to send my iPhone photos to Walgreens and Walmart for printing due to a format issue — the photos were in the HEIC (High Efficiency Image Coding) file format the iPhone uses. I then saved the photos in the JPEG (Joint Photographic Experts Group) file format the stores wanted, but I was told that some JPEG photos also aren't accepted. What can I do?

THOMAS ELWOOD, Bedford, N.H.

A: The photo printing services of Walmart and Walgreens require you to send them photos in the JPEG (also written as JPG) file format, which is widely used by digital cameras. The main restrictions are that Walmart won't accept any photo larger than 16 megabytes (see tinyurl.com/4ne5w4ha), and Walgreens discourages sending a photo larger than 20 megabytes (see tinyurl.com/pez3kt25). These limitations probably won't affect you; iPhone JPEG photos typically contain less than 10 megabytes of data.

The HEIC photo format (Apple's version of the standard HEIF, or High Efficiency Image Format) was designed to save storage space on iPhones. HEIC photos require only about one-third as much storage space as JPEG photos. The drawback to HEIC is that some photo-printing services and non-Apple devices don't use that format. So, since 2017 Apple has let you choose which format your iPhone should use for photos. To pick one, go to Settings, click on camera, then click Formats. Choose "high efficiency" for HEIC or "most compatible" for JPEG.

If you've already taken a lot of photos using HEIC, there are plenty of programs that can convert them to JPEG (see tinyurl.com/f3tkzd or tinyurl.com/373buv84). In addition, online file storage services such as Dropbox and Microsoft OneDrive can convert your HEIC photos to JPEG format when you upload the pictures from your iPhone.

Q: Until now, whenever I used my wireless mouse with my HP laptop, the PC's touchpad became inactive. But now the touchpad will not turn off, and this PC doesn't seem to have an enable-disable control for it. I've tried all the suggestions I could find online, but nothing works. What can I do?

PATRICIA TRAPP, Glastonbury, Conn.

A: It is possible to disconnect the touchpad. But first you need to make sure that your mouse is working properly. Otherwise, you could wind up with no way to access your PC.

Try reconnecting the wireless mouse to your PC to make sure it's set up correctly (you can search Google for step-by-step directions for your mouse's brand and model.) If for some reason the mouse won't connect, check to see if the mouse itself has been "disabled" on your PC.

To do that, use the touchpad to open Control Panel and click on "device manager." You'll get a list of all the devices on your PC. Scroll down to "mice and other pointing devices" and click on it. You should see two devices listed: Your mouse and something called "input device," which is your touchpad. Click on the mouse, and at the top of the resulting menu click the "driver" tab. Make sure that the mouse is "enabled" (if you're given a choice to disable the mouse, then it is enabled.) If the mouse still doesn't connect properly, there's something wrong with it.

Once you know the mouse is working properly, go back to device manager, click on "mice and other pointing devices" and this time click on "input device." At the top of the resulting menu, click the "driver" tab. Click on "disable device," then click OK.

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