Hoping a Lurker has a solution.

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When I go into the windows 7 disk to put it on the partition I have created for the OS. It runs through half a dozen tests or so, gets ready to install, and then gives me an error that it cannot install. The partition is clean, nothing on it.

By default Windows 7 likes two partitions, a small system partition to which it does not assign a drive letter, and a large boot partition for everything else to which it assigns the drive letter C. If you have not done so already I suggest using the Windows 7 version of Diskpart to format your partitions. Don't use anything else for making partitions. Diskpart is included on the Windows 7 installation disc. Boot from the Windows 7 installation disc, go to the command prompt and run Diskpart. You should also be OK just installing Windows 7 to a bare, unpartitioned drive if you don't care about drive letter assignments.

Here is what finally worked for me (as I have cut and pasted from an older post):

On the new hard drive create four primary partitions using the Windows 7 version of Diskpart from the 64-bit Windows 7 installation DVD. Let's call them 1, 2, 3, 4. Set partition 1 active.

Boot DOS 6.22 from a floppy and format partition 1 as FAT, transferring system files. We now have a bootable C drive and a DOS prompt!

Install Windows XP 32-bit on partition 1. We now have a working dual boot system. Because XP is 32-bit and Windows 7 is 64-bit, we can't simply install Windows 7 from XP. That would be too easy.

Set partition 3 active. Install Windows 7 64-bit from the installation DVD to partition 3. Boot into Windows 7. Format any as yet unformatted partitions and set up all the drive letters except C, which Windows 7 has selfishly assigned to partition 3, which by now you may have guessed is both the boot partition and the system partiton.

Copy the Windows installation DVD to partition 4 (just a convenient place to put it). Run Setup and install Windows 7 to partition 2, which is now the F drive. Boot into the new copy of Windows 7. All the drive letters are now correct except for partition 3, which is still C, and partition 1, which can't be C as long as partition 3 is C. See?

Remember partiton 3 is still the system partition, even though we now have partition 2 (drive F:) as the boot partiton. Use the Widows 7 utility Bcdboot to transfer the boot information to partition 1. Remove the drive letter from partition 1. Set partition 1 active and reboot.

We now have a triple boot: DOS, Windows XP, and Windows 7. Choose Windows 7. All the drive letters are as we left them. Partition 3 is still C, but since partition 3 is now neither the system partition nor the boot partition, the drive letter can be changed at will. I changed mine to L, and assigned C to partition 1, which previously had no drive letter assigned.

C is now my system partition and F is my boot partition, just as I've always had it for the past fifteen years. No registry hacks necessary. They said it can't be done. They being Microsoft forum folks. As in employed by Microsoft.