How do I change a system drive letter?


I have a PC that had XP Home installed on the C drive. I installed Vista HP on a second disk drive which is the H drive. Everything was running ok for a few weeks although the backup service for Win Home Server would not run - I was suspecting that this was due to some sort of problem on the C drive. I also wanted to make the h drive bootable so that I could remove the c drive in the future when I no longer needed XP. I temporarily added a couple of more hard drives to the system as I wanted to clone both the c and the h drives.

When I went back to the original setup I could no longer boot into Vista properly. When I ran the system repair on the Vista install I noticed that it seemed to think that my Vista install was on drive D rather than drive H. I tried going to the command prompt and changing the Vista drive letter to H using diskpart - I was able to make the change but when I rebooted it seemed to go back to the old letter mapping.

How do I force the drive letter on my Vista drive to be H? Presumably to work correctly it must be H as this is the letter it was upon installation and lots of things will be hard coded to this drive, will they not?
Are you able to currently boot into Windows?

The Vista repair program does not read the actual drive letters, it just guesses at what they're supposed to be.... Vista itself should still be H:
I am now able to kind-of boot into Vista. After the login screen it stops at a light blue screen. If I press Ctrl-Alt-Delete I am able to get to Task Manager where I can then run explorer, etc. But I can't run many apps, as it turns out under this scenario it thinks that Vista is on the E drive. When I try to run EasyBCD it tells me that the file E:\Program Files...\EasyBCD.exe does not exist - but this is when I click on it in an explorer window.

But when I run from the install DVD it still thinks Vista is on D:


One more thing - I can boot into XP which is still on my C drive and under XP the Vista drive is still H. I also tried repairing the Vista install but it says that there is nothing to repair.
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In Vista, what is Vista's letter?

Like I said, what the install DVD gives as the Vista letter is meaningless.
When I try to boot up to Vista the semi-working copy of Vista is using E but it is not at all a usable version of the OS. I tried running diskpart or diskmgmt from Vista but it tells me that the files don't exist even though they do - same thing when I try to run EasyBCD.
How do you know that it shows Vista as D:\ thru the install DVD? When i use Vista to install it doesnt give letter just partitions. So how can you be sure that it is registered as letter D:\ during the install process?

Have you tried to change the directory to H:\ and see if you can run these files. It seems that with all the changes that were tried to be made that something went very wrong.
If you Run/regedit then edit/find with the string ":/" (omit quotes) and untick "search on whole string" then F3 continuously, you can get a list of drive letters the OS has registered things to.
Once you have an idea of where windows is and your own 3rd party software is (or where the system thinks it is / used to be), it'll be easier to work out a strategy of how to recover things back to where you want to be.