Reestablishing drive letters (Win 7)

I have a laptop with XP installed. I installed Windows 7 (for boot loader purposes, essentially the same as Vista). XP on C:, Win7 on E: (DVD is D:smile: Dual boot worked fine. All well and good.

Then I accidentally mucked up the MBR and lost the partition table.

Fortunately a utility called "testdisk" can rebuild partition tables (yay!)

Unfortunately I still had to reinstall the boot loader. Did that with XP CD repair option. XP boots, but no Win7.

Tried repair with Win7 CD. Not so good. It tried to make the Win7 partition C: and the XP partition E:, then complained because my Win7 was "not genuine" (Well, you'd find what you were looking for if you set the W7 partition to E:!)

Moreover, since it thought the XP partition was E: I could not even boot XP with that loader.

Ok, repair again with the XP CD. Now I'm back to square two: XP boots, but no W7. Is there any way to put the W7 (i.e. Vista) boot loader back on but have it understand that the system drive (the W7 partition) should be referenced as E:?

Thanks in advance.


Knows where his towel is.
Staff member
Hi rm, welcome to NST.
Don't worry about disk letters, they're not physical, just an internal construct of the running system - entries in its registry.
Each booted system will have its own internal map of what all of the partition letters are, and none of those maps have to bear any relation to what any of the other systems have mapped.
The booted DVD is an OS in its own right and will assign letters too. It doesn't have any effect on the registry of the systems it sees. Those systems when repaired and booted will still see the world as they saw it before.
There's no point in repairing the boot with XP in an XP/Longhorn mix. XP PBR has to be replaced by longhorn's. The boot process is only backward compatible, with Vista/W7 able to boot XP, not the other way round.
You must repair the boot with your W7 DVD (3 times), and if you're getting "winload invalid digital signature" it indicates another problem, nothing to do with disk lettering.
Do you have a RAID setup ? This problem can occur with that, or possibly because your W7 boot files have got put somewhere unexpected.
Have a read of these two threads, where users had similar problems to see if you recognize anything.
I think you misunderstood. When I installed Win7 the first time, it understood that it's partition letter was E:. When I tried the repair, it somehow got the idea that it's partition letter was C:. This means that all the registry entries using E:whatever to point to system files are not finding them because they are now on what the os things is C:. I need the boot loader to boot up win7 with the understanding that the system drive letter is actually E:. I know the letter assignements are internal to the os, and that xp and win7 might have different letters ... but right now win7 has the /wrong/ letters.

I will check out those other threads you reference.

worst case, I can reinstall win7 from scratch ... but then I would lose the applications and such that I had installed there and I would rather not have to go through all that if I can just convince it to use E: as it's system drive letter....


Knows where his towel is.
Staff member
Don't panic, just do this


New Member
Hi, I have just been passing through mostly the same problems as this guy, and hopefully (having read this topic) I was able to get my "Vista and Win 7" back dual-booting correctly (using registry to change the boot drive letter in Win7).

However while editing Win7 registry, I've found a unknown drive:

C: Unknown (18 .. 00 00 b0 10 ...)
H: Win7 (18 .. 00 00 b0 90 11)
K: Vista (18 .. 00 7e ... )
G: Drive (5c......)

What I did is rename "C to D", "H to C", "K to E" and my Win7 could finally boot successfully.

1. Using Win7 built-in 'disk management' utility I've changed the "(Vista) E: to D:" for convenience.
2. Then I remembered this unknown entry I saw in registry, I checked it out but it had already disappeared.

I was wondering if someone might know/estimate what that entry was?

Notes: Win7 was installed on an extended partition.

Also, as the other guy, my problem was that 'Win7' was loading partly saying it was not genuine with some references to irrelevant drive letters.
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