How to change drive letter designation outside Windows 7

I have a friend's laptop running W7 64bit. It was essentially unusable simply getting a blinking cursor on boot. I've run some diagnostic etc but gotten the no OS found message.
On further repair attempts found what I believe to be the issue. The drive letter designations are all messed up. It is trying to boot from C: but C: is the "system reserved" drive. The real C: has a drive letter designation of D:
I believe the fix is to change the drive letters back to the correct drive.. How can I do that from outside Windows?
Any thoughts?
Thanks for any help
Monton

This is a symptom that the partition table is damaged and the direct approach (ie trying to change drive letters) is not the right way to fix this. you need a tool to fix the partition table.

I wondered if the owner had something, external drive, camera, etc. plugged in and rebooted and replaced/unplugged/plugged in something during the boot or reboot and that caused the drive letters to get "bumped". I haven't been able to to launch a recovery from the hard drive either. Probably has to be launched from C
Do you have a favorite partition table tool? A suggestion?
Thanks for the reply and help
Monton

Sorry - - not my area of expertise. Stand by, there are those here at Techspot well versed in this issue.

On the one hand, EASUS Partition Master has a reasonably straight forward User Interface. There's a free version but it doesn't include a bootable recovery CD (which you'd need). The paid version is $39.99

HOWEVER, IMO yours can be a "murky" kind of problem and still not easy or straight forward to fix with a Partition Tool. Do you have the Windows 7 x64 install disk? I see a few other options

1) You might first try recovering/backing up the user data before you proceed.
How to recover your folders/files when Windows won’t boot

2) Use the Win 7 disk to try a Windows 7 "repair" http://windows.microsoft.com/en-US/windows7/products/features/startup-repair

3) If that fails and you have the user data backed up, you might be best doing a clean Win 7 reinstall

fyi... Some info you might find useful about the partitions you're seeing http://technet.microsoft.com/en-us/magazine/gg441289.aspx. That first partition shouldn't be bootable and somehow got screwed up.

Good luck!

One more thought / comment:

The "C" drive is the first bootable partition on the hard drive. That system partition shouldn't be bootable. In which case, the computer would boot from the second partition and it would become "C". Somehow, that system partition must be marked the Active boot partition, so it becomes the C drive and Windows trys to boot from it, but there's no OS in it so you get that message.

With that chain of thought, I suppose you could also try a bootable partition recovery CD and make sure it's the second partition is the one marked "Active"

Thanks for the suggestions. I tried to use Part Magic but was unsure of trying to change or even sure if I could change drive letters there. Part of the problem of the scrambled drive letters was that I couldn't access the Sony recovery program to do a destructive recovery since it had to be done from C. The system reserved partition had become C and the active partition became D and not active.
(Note, the laptop owner said there wasn't anything on the drive that she needed so a fresh install was okay)
I pulled the drive and put it in a desktop. I used disk management to change drive D to active and changed C (system reserved) to G
Put the drive into the laptop and received the message that Boot Manager was missing and to reboot. On reboot I was able to launch recovery and am currently accomplishing that. I think all will be fine in the world soon.
I may have been able to change the "D" back to "C" but was happy to do a fresh install anyway. If I run into problems - I'll be back!
As always thanks to those who responded
Monton