As you know, stupid setup.exe for nt 6.x (vista/win7/2008/2008 r2) has many limitations:

1. You can't start install vista/win7 under xp based pe (winpe 1.x) and can't install win7 under win2000
2. You can't install win7 directly to USB hard disk
3. The stupid setup.exe may put the boot files to a wrong drive when you boot winpe with USB device and there is even no way to choose the boot partition 
4. When you install win7 from winpe, the drive letter of the OS partition will always be C:, no matter which partition you choose.

On the other hand, the fastest way to install nt 6.x is imagex+bcdboot, e.g

CODE
imagex f:\sources\install.wim 5 c:
bcdboot c:\windows /s c:
bootsect /nt60 c:


And no setup.exe is needed.

Based on this, I wrote an "nt 6.x fast installer" which has the following advatages compare to the original M$ setup.exe:
1. You can install nt 6.x directly from iso file mounted by any kind of virtual drive.
And you needn't extract or burn the iso.
2. You can directly install nt 6.x from any version winpe and win2000 above windows
3. You can install the OS directly onto a USB external hard drive.
And no virtual machine, copy tool or complicated "tutorial" is needed.
4. You can manually choose which partition is the boot partition.
5. You can decide which letter the OS partition will occupy in Win7/2008 R2.
6. The install speed is very fast. With this installer, you can install win7 in 11-12 min for 5400rpm notebook hdd, and in less than 10min for desktop 7200 hdd (vista needs about 2 min more because of the score evaluation)