Q: How can we stop the annoying Amazon lock screen advertisements that are plaguing our iPhone and iPad Safari browsers?

George Adams, Merrimack, N.H.

A: You aren't seeing the Amazon lock screen ads. Those appeared only on the lock screen (the screen you see before typing in a password) of some non-Apple phones that Amazon sold.

The ads you are seeing in your iPhone and iPad Safari browsers are caused by unwanted pop-up software that comes from many sources, some legitimate and some not. Some of these ads try to sell you something, while others — typically those that deliver warnings or offer prizes — are "phishing" scams that try to trick you into disclosing personal information.

To avoid getting these pop-ups, make sure your Apple iOS operating system is up to date (some updates enhance security.) Go to Settings, click General and then click "software update."

You should also make sure that your Safari browser is set to enable the features "block pop-ups" and "fraudulent website warning." To turn them on, go to Settings and click Safari. If the pop-ups persist, go to Settings, then Safari, and click "clear history and website data."

Q: I read your article on ransomware, the malicious software that can encrypt the files on a PC and keep them locked unless you pay to free them (see tinyurl.com/ybq6zm22).

What happens if, as you suggest, I unplug my external backup device to protect it from ransomware, then plug it back into the PC after a ransomware attack so that I can restore my files? Would the backup device also become encrypted by the ransomware?

Lyle Behm, Apple Valley

A: It's possible. If you have a ransomware attack, you should use security software to remove the ransomware files from your PC before plugging in your external backup device.

If the PC won't let you install anything, force it to restart in Safe Mode (see tinyurl.com/hahn2u4). Then download and run the free version of Malwarebytes (tinyurl.com/jsdacdk) and the 30-day free trial version of HitmanPro (tinyurl.com/jfxatff) to clean your PC's hard disk. Then use Windows System Restore (see tinyurl.com/kxanto5) to return your PC's settings to the way they were on a calendar date before the ransomware attack. After that, it will be safe to reconnect your backup device.

Q: Following the installation of a "critical update" on my Windows 7 PC, I'm unable to access my files. When I log into the PC, I get a message that says I'm a "temporary user." Using System Restore didn't help. What can I do?

Mark LaFond, Bemidji, Minn.

A: The Windows 7 update has corrupted, or scrambled, the "user profile" that stores your login information. As a result, you will need to create a new user profile that will give you access to everything on the PC. First, log in as an "administrator" (see tinyurl.com/y7bcejuq and go to "cannot log in/no other user account available.) Then set up a new user profile (see tinyurl.com/yctk6dc3 and follow the instructions for "my computer is on a domain.")

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.