While installing the 1st OS, you will be asked if you want to delete everything, keep it the same, partition ect.
Choose partition. Hack up your hard drive as you see fit. If I only had a 250 (shudder) I would break it up as 50gb C, 51gb D, the remainder E (Something like 147gb). (Make all sizes different so that you can easily identify the partitions even if they are labled wrong.)
Install the First OS on C, set it up nicely.
Restart and instal the second OS on the unused partition that is 51gb.
If you automatically boot into one without an option to boot into the first, then go to Start>run>msconfig
On a new computer, I will have two hard disks with
250GB each. I would like to install one XP Pro and one XP Media Center Edition. If possible, will each
operating system has a seperate registry for each.