I have an old 531 desktop that has almost 10 years of files. I have upgraded it to 64bt Windows 10 so all of the support programs from Dell don't work.
I would like to keep it and put any money into a laptop. However, programs such as Tweaking.com seem to make it worse. Funds are tight right now, so I need to keep this running. It's slow but I only use it for internet. No gaming. It crashes a lot. Has a hard time with flash websites.
Assuming you went from Windows Vista to Windows 7 to Windows 10... with each upgrade leading to a performance loss... The best thing for you to do is a clean install of Windows 10. You'll need to backup all your files to an external hard drive before proceeding.