The least painful is right. For me, that would be to use a utility such as Partition Magic to resize the partitions, adjusting the sizes as you wish. That would adjust the amount of space available on the partition used by each installation, which is what I believe you desire. You could also modify boot.ini in order to change the boot order, making Windows 2003 your primary boot. For information on that, click here.
My second choice would be to backup all files, wipe all partitions, then start over any way you wish. That's certainly a long and tedious way of going about it, but still a valid method.
Hope this helps,
I have been experimenting with multiple windows installations on a computer and ended up with the following:
1. On disk C, a 60 Gb disk, I have my main stay Windows 2000 prof. installation,
2. On disk D, a 5 Gb disk, I have a windows 2003 enterprise installation that I intend to make my main isntallation, and
3. On disk E, a 29 GB disk, I have a windows xp spanish installation that I use only to be able to advise some family members that use windows XP spanish.
I would like to move the 2003 installation to disk C, the XP installation to disk D, and the 2000 installation to disk E.
I also have an USB 300 GB drive for backup and data storage purposes. What would be the least painful way of accomplishing the moves?
Thank you very much for your help.