Q: My HP PC (an Envy x360 m6) is running Windows 10 Home with all the current updates, and I use Norton antivirus and the Malwarebytes security program. But over the last year the PC has really slowed down when it comes to starting Windows or programs. Even after starting, many programs run slowly. My PC has 8 gigabytes of RAM (computer chip) memory and a 1 terabyte hard drive that's about 80% full. What can I do to speed up the computer?

Gary Brown, St. Paul

A: You have nearly filled up your hard drive, which is probably causing the speed of your PC to drop off dramatically.

Why? When a drive fills up, the available storage spots become smaller and are scattered across the disk. So, when the PC stores files on the disk, it has to split them into pieces and store the pieces in different locations. This slows the storing process and creates a disk condition called "fragmentation." The next time these fragmented files are needed, it takes extra time for the PC to locate, read and reassemble them. Fragmentation becomes a serious problem once the hard drive reaches 80% full.

You should either get a larger hard drive, shift some data to another drive or just delete some data. Once you have freed up more disk space, you can use the Windows "defragment" feature to copy the scattered files into single locations (see tinyurl.com/y5os4pql), which will improve PC speed. Note that defragmenting a hard disk can take hours.

While freeing up disk space will probably solve your slowdown problem, there are a few other things you should check as well.

• Make sure there is no unwanted or malicious software on your PC. Update and run Malwarebytes.

• Check to see if any programs are using a large amount of the PC's processing or RAM memory. Open the PC's Task Manager (right-click the menu bar at the bottom of the screen and select Task Manager from the list.)

Under Task Manager's "apps" heading, you should find only the programs you are currently using. Under "background processes," you will find things such as iTunes and the Windows digital assistant program Cortana, even if they aren't being used. You can temporarily turn off some of these app-related background processes to see if it causes a problem (they will automatically turn back on when you restart the PC.) To temporarily turn off a process, left click the name in Task Manager, then right click it. From the drop-down menu, choose "end task." To permanently turn off a process, remove it from the PC's startup menu (see tinyurl.com/y4jyh4xs option three.)

Q: Now that we've updated to Windows 10, what's the best way to erase the hard drive on our Windows 7 PCs before donating them?

Lana Luhm, Eau Claire, Wis.

A: You raise a good point. Windows 7 PCs shouldn't be donated unless the hard disks have been wiped clean, including erasing the operating system. Then either Windows 8.1 or 10 should be installed by you or the organization to which you are donating. There are several ways to erase a hard drive (see tinyurl.com/hrdk248). Or you can install a new hard drive and destroy the old one. Drilling a few holes through the case effectively destroys an old drive.

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