Said DELL is several years old. Win10 inside. The file system occasionally refuses to work. Windows explorer I think is what is is.

Most of my files go onto an outside Seagate Backup Plus Drive via USB. One Terabyte I think. Just looked. It has 846 GB free in it. OS (C) has 398 free. So it is not over loaded.

Also my Open Office sometimes wont load. Turning the whole unit off then on fixes it.

I need a DELL doctor I guess

I wish Windows would stop upgrades on Win10 that work fine. I.e. If it ain't broke, don't upgrade it.

Sounds like the hard disk is dying. You can just replace that for much less than the entire computer. In point of fact, unless you're doing some very computationally intense work on the computer, a new computer isn't going to be able to do much more than a few year old one.

I'm typing this on a 10-ish YO tower PC I built myself. A few components have died over the years, and I've replaced them. The SSD died right around the time that Microsoft EOLed Windows 7. So I took that as an opportunity to move to Windows 10. The machine still does everything I need it to. If I run into something I need it to do that it can't, I'll either gut renovate it (motherboard, CPU, and memory), or just replace the whole thing.

If you have a good back up, last resort is to reformat and start anew. The dell utilities or disk have this function. I've done this to two different Dells with good results. They run like new machines, although you need to redo a lot of settings just like when you got your PC new in the box. It should be last resort because it's a PITA.

You can use chkdsk to see if errors are occurring on a hard disk. I wasn’t clear on whether you’re always booting ok and then getting file system errors or having booting problems. If the latter, don’t forget to check the lithium battery on the motherboard; they go after a while and create bootup issues.

And to add, if you don't have an SSD drive, go for that if the drive is actually failing. 1 gb should be about $100 and if you don't feel comfortable about installing hardware, your local computer guy shouldn't charge more that $100 or so to do it. Much cheaper than buying a new PC and you'll be amazed at how quickly it boots and transfers files. Like night and day from a spinning drive.

Some old systems can be revived and given new life but it really depends on what it is.
I draw the line at Intel Gen3/4 ~ any older is a no go.
It has more to do with the hardware technology and not the OS albeit everyone love to bash it first.
Yes, SSD is one part that can help breath new life in an old system.