Windows 7 Drive letters switched

[selfgov2000]

My computer had Vista Ultimate on Drive C, and XP Pro on Drive D (dual boot). I wanted to upgrade to Windows 7, and couldn't upgrade from Vista Ultimate to Windows 7 Professional (which is what the Action Pack CD is). I purchased Laplink PcMover Update and ran it on the XP installation then did a custom install to drive D without a format. When Windows 7 came up, it had switched the D drive to C, and the C drive to D. Not only does that not work to complete the PcMover process, It would be a nightmare to try to convert everything on my drives to work with that situation.

Why does 7 think it needs to be on C regardless of what it messes up, and how do I rectify this (re-switch the drive letters within Windows 7)? I can still boot to Vista, and the drive letters are what they are supposed to be.

Thanks,
Dave