I’ve downloaded about 10 gigabytes of arcade game software updates to my used PC, a Dell Latitude E6400.

Recently the PC has slowed down, and I discovered that its hard drive was nearly full (probably the previous owner left some data on it).

Which files should I delete?

Clearing files from your relatively small 160-gigabyte hard drive should speed up your PC.

As the disk fills, the PC will break up files into fragments to be kept in the disk’s smaller spaces. But it takes the PC longer to reaccess such files. In addition, antivirus software takes longer to scan a nearly full hard disk, which absorbs processor time.

You can clear space on the hard disk by deleting data or uninstalling non-Windows programs. But don’t get rid of any files that are needed by Windows or the programs you regularly use.

Here’s a list of things that you should never delete: (for details, see tinyurl.com/yb7kjotd):

• “Program files” folder: It contains your PC’s programs and the Windows system files that allow the programs to work.

• “Windows” folder: Everything in this folder is needed to keep Windows running.

• “System32” folder: Located within the Windows folder, it contains vital operating software that handles things such as starting up your PC.

• “WinSxSCQ” folder: It contains software that makes older programs compatible with your version of Windows.

• “System Volume Information” folder: It helps “partition” or divide the hard disk into sections, and has the data for “system restore,” which can roll back changes you’ve made to your PC.

• “Pagefile.sys” file: If your PC’s RAM, or computer chip memory, gets full, some of the data spills over to this file for temporary storage on the hard disk.

• “Swapfile.sys” file: If your PC goes into “hibernation mode” when it’s not in use, any data that was stored in RAM will be shifted to this file on the hard disk.

If the PC still runs slowly after deleting hard-drive data or programs, you may need to increase the amount of RAM (your PC came with 2 gigabytes of RAM, but can use up to 8 gigabytes). RAM is where the PC stores data that it needs to access quickly for an ongoing task. If the RAM is full, its data spills over to the much slower hard disk (see “Pagefile.sys” above).

I previously had a photo slide show running in the background on my Windows 10 PC. Then I deleted the photos and switched from a slide show to a single picture in the background. Now the background keeps reverting to a slide show with the same photos I deleted.

How do I stop this?

Hold the Windows and I keys down simultaneously. Click on “personalization.” On the next menu, click the drop-down menu beneath “background.” Change the selection from “slide show” to “picture.” From the “choose your picture” menu, select the photo you have already chosen to replace the slide show.

The deleted photos probably reappeared because they were copied for the slide show and still exist on your PC. To make sure they aren’t displayed, turn off a Windows 10 feature called “linked duplicates” (go to tinyurl.com/y74mj3nd and scroll down to the screen shots).

Steve Alexander covers technology for the Minneapolis Star Tribune. Readers can email him at steve.j.alexander@gmail.com. Please include a full name, city and phone number.

Tribune News Service