Q: I use the Mozilla Firefox browser on an older desktop PC. Lately I’ve noticed that the browser has been slowing down when it loads Web pages. Do I need to run a program to clean malicious software from my PC?

Dan Fabeck, Minneapolis

 A: No, it’s a browser problem. Technical issues with Firefox are causing it to lose speed. That’s too bad, because for years Firefox was the preferred alternative to Microsoft’s Internet Explorer. These days I recommend Google’s Chrome browser (download it at tinyurl.com/leg6y44).

There have been many complaints from Firefox users that the browser is slowing down (see tinyurl.com/l72l55d). While there appear to be several causes, there are two primary ones: Firefox sometimes uses too much of your PC’s memory, and it has trouble handling websites that extensively use Adobe’s Flash software for animation.

Partly as a result of Firefox’s problems, the Chrome browser has overtaken Firefox as the second‑most popular Web browser. Microsoft’s Internet Explorer remains No. 1, although that may be partly because it is included with Windows, while the Firefox and Chrome browsers must be downloaded separately. In July, Firefox had about a 15 percent market share, compared to about 20 percent for Chrome and 58 percent for Internet Explorer, according to market research firm Net Applications (see tinyurl.com/n8gmkf2 and click “continue to site”).

 Q: My daughter recently bought an Asus netbook PC that the previous owner had upgraded from Windows XP to Windows 7 Home Premium. The only problem is that she can’t install new Windows 7 updates; she gets the error code 80070490. Microsoft’s online support couldn’t get the update to work, either, and suggested that she reinstall Windows 7.

What’s causing this problem, and is there any way to fix it without reinstalling Windows?

Harold Schuf, Eau Claire, Wis.

 A: The error message you received means that a Windows file that installs updates is corrupted, which means it must be fixed or replaced.

Fixing the file is preferable to reinstalling Windows because the fix won’t affect the data or the programs on your PC. First try Microsoft’s automatic reset software for Windows 7 and 8, which can be run from the Microsoft website at tinyurl.com/ls6hhr.

If that doesn’t work, you have two options: repair or reinstall, both of which require you to have the Windows 7 installation disk. (Because you’re dealing with a netbook, you’d need to use an external DVD drive to run the disk.)

You can try the available repair options, although they don’t seem to apply to your problem (see tinyurl.com/qyhd8g7). If you reinstall Windows 7 using the original disk, you must first save your daughter’s data on a flash drive or external hard drive. Then, after reinstalling Windows 7, you’d have to reinstall the PC’s programs and restore the data.

E-mail tech questions to steve.j.alexander@ gmail.com or write to Tech Q&A, 425 Portland Av. S., ­Minneapolis, MN 55488. Include name, city and telephone number.