Virtual XP closes down immediately after start-up

For about 5 years I have been successfully running Virtual XP under W7 Pro x64. Several of its applications also ran remotely under W7 itself.

After being away for two months at the beginning of this year, I tried to run one of the remote applications and received a message that Virtual XP was not running. So I tried to restart Virtual XP itself. It seemed to be working:

1. The Virtual XP window appeared
2. A message said that my settings were being loaded
3. The desktop icons appeared
4. But then if I:
   
   1. moved the mouse
   2. or simply did nothing for a couple of minutes

• it simply closed down without any message!

This has continued to happen every time I start up Virtual XP or any of its remote applications.

• Why?
• Can I do anything about it?

Virtual XP has become essential for me. I wrote several of my own applications in Turbo-C under MS-DOS almost 20 years ago and I still use them. But of course they will not run directly under Windows 7. Recompiling them is out of the question as the original compiler is also an MS-DOS application.


I know there are alternative ways of running them, but I have tried out Dosbox and looked at VirtualBox and they are not promising.