Hi Sally,
I recommend you upgrade to FP2.6a/DOS. It is much more robust.
One of my clients is running a fairly large and sophisticated FP2.6a/DOS system in a DOS window under WinNT 4.0 and it seems to be running fine. I don't think it's a good long term strategy, but for the short term it seems just fine. I don't know if the same is true of FP2.0/DOS.
Regards, Chaim