IIRC, since I go way back with this game... it had something to do with the computer name being different compared with current computer and what's in the savegame file. If the two aren't the same, the game won't see them.

Question, is the version number on the Options screen 1.5b?

Ok, I also have Version 1.5 and after a few test on my older PC, I have the solution:

My old saves where from the European Version of Darstone and these saves are incompatible with the US Version. Damn it, now I have to start again....

Also there is only one tool which works to move the saves to a PC with another name: Darkstone Chartrans. The other tool "DSfix" only works for the European Version.

Sorry to hear that you couldn't use your saves! 8(

Yeah, I have a copy of the Euro version, but I did all my building and playing with the US version.

There's a fix utility still out there that fixes character files (not game saves unfortunately) and you can find it by searching for: "Darkstone Fix v1.0 (Chartrans)" but because it won't do saves, I don't recommend this solution, but it DOES give me an idea...

Change your machine name back to what it was when you were last playing Darkstone for the duration of playing the game. (This could pose a problem for machines that are members of domain.)

Maybe build up a Virtual machine by that machine name and play it in that?

Getting the old machine name if you don't remember it:

Use a hex editor (or even Notepad) to open up the characters.lpl file, or the .sav (game save) files, the machine name is prominently there in the first few bytes.

Thanks for the help everyone.
I got all the tools to change the character names.

Unfortunately, there is no tool to compile european characters to the us version.
They are incompatible and thats not a problem of the computer name.
Opened in an Hex Editor, the save files are extremly different, except the computer name :-).

I think this issue is done. I marked the link to all the helpful tools as a solution for other users.