I have a Windows 7 machine on which the XP mode does not remain available.
I have checked to make sure BIOS allows virtual machines. It does.
I followed the same install procedures as I have done on other installs of XP mode on Windows 7 machines.
I installed the XP Mode in administrator mode.
However, when I switch to the specific user's session, XP Mode does not appear in the list of virtual machines.
When I uninstalled XP Mode from the administrator session and installed it using the specific user's session, it "re-installed" every time I rebooted or logged off. Anything I had installed inside the XP Mode would be lost.