Sorry I can't answer your question. But I just want to add that Vista actually loves being the second OS. As long as you install it to a different drive or partition it sets up a dual boot, leaving xp intact. I really doubt they would change this behavior for windows 7. MS really wanted to make it easier for people to test the OS before committing to it.
i tried dual booting but had some issues, so ended up disconnecting my main drive and installing on the spare, just made things easier and means i dont have to worry about win7 installing stuff on my xp drive.
If you tried Build 7000, you don't need to boot from it. Just format a partition as NTFS, and mount a the ISO (or pop in the burnt disc), while still running XP. From there is will start the install, and when it restart you no longer need the disc and it will finish the install.
Working with XP and 7 on same hard drive on different partitions for some time didnt have any problems,the bootloader 7 uses is far better and advanced then ntldr XP file.Also any issue about dual boot can be fixed in 7 with BCDEDIT /? from command line
The document only covers XP, but you'll be 99% of the way there and it will catch all your mistakes, my guess is MS won't change much and booting 7 will be much like it is for XP, you will have to do some checking to see if hexediting the first sector of the partition still matters.
Portlock Leap Frog does this easily, no second hard drive needed, the local hard drive does not need to be partiioned. Its easy and quick.You can keep both XP and WIndows 7 or Vista for that matter and have a dual boot system.