Preview Icons Not Displaying, Sometimes No Icons Display in Explorer

After progressively getting worse, Windows Explorer now displays as seen in the screen shot (no icons are displaying). At first I thought it was taking time to build the icons, but it never does. the loading bar stays loading at 90%. The first few times it happened, I thought I was in a folder with a lot of previews to build in it. Okay. But then it never built the previews. Then for a while, it would load previews for a few minutes after the computer restarted, and then stop displaying those previews. Now it's immediate. I have no icons displaying. Well, in some folders it decides to show the generic icon for the file type (i.e. generic picture icon for png files) instead of building previews. And other times I have a folder mixed with files that display a preview and files of the same type that display either no icon or the generic file type icon.

Even the list view does not display file type icons, and changing the icon size doesn't matter.

What could this be?

(I already deleted the "IconCache.db". It did nothing.)

Thanks for the response and suggestions. I have an IBM laptop with 8 GB of RAM. Since I'm able to go about my day-to-day with the problem, it's low on the list of things to address (and why I haven't touched it in a week). It's also why I kind of doubt I have bad RAM, but I'll try it anyways. I've learned that everything requires testing when it comes to identifying a PC problem! I will try the Memtest86+ either tonight or tomorrow night, and update you Monday.

Again thank you!