More memory and a SSD would most likely help a lot.
If it is difficult to upgrade it might help to use the ReadyBoost feature in Windows. You can configure Windows to cache the HDD using a USB stick. May be much faster than a mechanical HDD and at least it is very easy and cheap to try if you have a USB stick handy. How good it works depends on how modern USB the PC has and how good the USB stick is.
I donated a 8GB SanDisk USB 2 stick to my dad with an older PC with USB 2 and Win 10, to use as ReadyBoost. He was about to buy a new PC after upgrading to Win10. It helped quite a bit so no need to buy a new PC or upgrade.
https://www.techcrises.com/how-to/in...ve-windows-10/
https://www.techrepublic.com/article...in-windows-10/
https://www.techrepublic.com/blog/wi...-in-windows-7/