Attempting to start a new game after Mission Selection results in being kicked back to the command prompt with the message:

Fatal error number:50 File:Error writing to disk, possibly write protected.

The game is trying to create PROFILE.688 but can't for some reason. It's stored in a directory on my hard drive, which is obviously not write protected so that's not the problem. I have plenty of hard drive space available.

The problem is 100% reproducible. It happens every time, regardless of which mission I select.

I'm running DOSBox 0.63 under Windows XP/2GHz P4/1GB RAM.