Today I needed to swap motherboards between a machine running Hyper-V Server 2008 R2 and another running 32-bit Windows 7. No need to go into the reason in detail; it’s to do with some testing I’m doing of Hyper-V backup and restore. The boards were similar, both Intel, though one had a Pentium D processor installed and the other a Core Duo. Anyway, I did the deed and was intrigued to see whether Windows would start in its new hardware.

Hyper-V Server – which is really 64-bit Server Core 2008 R2 – started fine, installed some new drivers, requested a restart, and all was well.

Windows 7 on the other hand did not start. It rebooted itself and offered startup repair, which I accepted. It suggested I try a system restore, which I refused, on the grounds that the problem was not some new corruption, but that I had just changed the motherboard. Next, startup repair went into a lengthy checking procedure, at the end of which it reported failure with an unknown problem possibly related to a configuration change.

That was annoying. Then I remembered the problems Windows has with changing to and from AHCI, a BIOS configuration for Serial ATA. I posted on the subject in the context of Vista. I checked the BIOS, which was set to AHCI, changed it to IDE mode, and Windows started fine. Then I made the registry change for AHCI, shutdown, changed back to AHCI in the BIOS. Again, Windows started fine.

What puzzles me is why the long-running Windows 7 startup repair sequence does not check for this problem. If the alternative is a complete reinstall of Windows, it could save a lot of time and aggravation.

It is also worth noting that Windows 7 declared itself non-genuine after this operation, though actually it re-activated OK. I guess if you had two machines with OEM versions of Windows 7, for example, and swapped the motherboards, then strictly you would need two new licenses.