Are you interfacing with any old printers or other hardware? You might be able to run things in a virtual machine instead.

I know you mentioned not wanting to move to modern systems. But a VM could run Win98 and your current software. It would also be portable so you're ability to invoice clients wouldn't need to rely on keeping 25+ year old systems up and running.

Thanks for the tips. Not using any old hardware, just standalone for files. Tried VMs before, but this software needs direct hardware access to run right. Had database issues with emulation in the past. Need to get the CF card issue sorted on the actual machine. Actually, I was looking at https://ultrastrategy.com earlier for some similar hardware fixes, might find something there.

I'm not sure what database solution, or when you last tried it. But virtualization of large databases servers happens in some of the largest companies today. You could always give the VM direct access to the disk, though you really shouldn't need to.

You mentioned handling a lot of small files and longer sessions. How long are you leaving this machine running, and roughly how many files are we talking about? I wouldn't expect an account application to go too crazy like something doing some very heavy processing and opening tens to hundreds of thousands of small files for processing. But you never know.

A CF adapter should work more or less like a regular HDD in terms of interfacing. When's the last time you tried running this directly off an HDD? It's possible hardware isn't the issue at all.