Changing Driveletters in XP Pro after reboot

Hi All

I'm having a small but annoying problem with the driveletter settings in XP.
This problem is occuring for some time now and with different XP Pro versions and different
installations.

The problem is that my virtual drive(s) SOMETIMES change after a reboot to the next available
driveletter in the system in stead of the driveletter I set it to.
The way I set the driveletters, either with the used program or by Windows XP itself, makes no
difference.

At the moment I'm using DVDfab Virtual Drive but the problem occured also with Nero ImageDrive
and with Magic Disc.

Sometimes I can boot 10 or more times with no driveletter changes and sometimes 2 or 3 times in
a row the problem occures.

All the other driveletters always keep their assigned letter, also the USB-devices wich use the
last 4 letters of the alphabet.

Anyone any ideas ???

Thanks in advance, Tom