Hi Lona
When it comes to talking about drivers, I quickly find myself out of my depth. Nevertheless, I have a HP815C myself that's been giving me faithful service for years. I connected it to my computer when the computer was new, running the original version of XP. Of course, the OS has since been upgraded through Service Packs 1 & 2, but it's still chugging along.
I've checked the original driver disk that came with the printer and the software doesn't appear to be very large, about 100k. The files are named COMPINFO.TXT, HPDJ815C.INF, HPF21.HP, HPFPNP.DLL, HPFPNP.INI, HPRDY.HP, HPSETUP.INI, SETUP.EXE and VERINFO.TXT. I don't know which file is the driver, but I'd be happy to email all or any of them to you if it might help.
Gill