would LE 4 project files open on later versions?

My Vista machine (circa 2008) has died, it happily ran Cubase LE4 which came bundled with a Tascam digital interface.
If I buy a new LE now for my Windows 10 machine, will it open the projects? (which I have sensibly backed up!)

Normally yes. Cubase will open files it created almost all the way back to the beginning.

Best thing to do is download the Elements trial, and check it out.

If you upgrade to Cubase Elements 9.5, you can run Cubase Elements 8 which should be able to load all of your old projects without issues. Using Cubase Elements 8 is only necessary if you used 32 bit third party plugins.

Compared to Cubase LE 4, Cubase Elements 9.5 is a lot easier and more intuitive to use, and it adds a ton of new stuff. I think you’ll like it quite a bit once you get used to the changes.