I recently upgraded a Windows system from XP to 7. XP was on an internal SATA disk and I added a second internal SATA disk for 7. Since there is no painless upgrade path from XP to 7, I resigned myself to reinstalling all relevant apps and copying user data over myself. This went pretty smoothly... until I decided to decommission the XP disk.
It turns out the 7 installer had spread what I thought would be a clean installation across the XP and 7 disks. The XP disk had a 'boot' directory and a file called 'bootmgr' and the 7 disk had the rest of Windows. This scheme is apparently what allowed me to choose XP or 7 at boot time. As soon as I disconnected the XP disk from SATA, the computer unsurprisingly would not boot.
Don't ask me how I figured out what the problem was, because it was a little bit of googling and a little bit of guessing and a little bit of luck. In any case, I copied 'boot' and 'bootmgr' from the XP disk to the 7 disk and then used a repair feature of the 7 installation DVD to write a proper boot sector onto the 7 disk and link it up to the files I'd copied. (At least that's my limited understanding of what I did.) The computer now boots 7 without the XP disk.
My question is borne of paranoia. Given the guessy/lucky "manual" way I managed to accomplish this, I expect there is some detail I missed. Though the computer boots and seems to work fine, I don't want to find out later the hard way that I can't easily restore a backup or pass some Windows Genuine Advantage test or something like that. Is there something more I should have done?