Here's my experience with not reinstalling Windows 7 for motherboard replacements:
My motherboard died about 5 weeks ago. I had no choice but to replace it. I went from one Intel/Asus motherboard and processor to another. (Asus P5Q Pro Turbo with Core2 Quad Q9300 to an Asus P8P67 ver. 3.0 and an Core i5-2500). The new board has DDR3, SATA III and USB 3.0. It also has a UEFI BIOS. The old board had VIA audio and the new one has Realtek. So it is still Intel, but quite different in many respects. I never even removed my hard drive from its bay. I had no problems. I had a little clean up to do to get rid of the old audio control panel. I did no repair install. Just booted right up except for one screen that asked me if I wanted to discard my settings (it never woke from hybrid sleep when the motherboard died). It has been 3 weeks and I'm posting from the computer in question. My typing is still lousy, but Windows 7 is fine. I did some clean up that I'm not going to go into detail about, but that was because I wanted to, not because it was unstable or blue screening or anything like that.
So my husband sees my speedy new rig and he decides his 4 year old stuff is getting pretty slow. But his change is even more dramatic. He goes from a dual core AMD processor on a board with an nVidia chipset to the same board and processor I got. He did have a SATA drive but he had never run it AHCI. He also cloned his drive using Acronis 2010 to a new 1TB SATA III drive. That was the only hang up. He forgot that he had to change that setting. When he changed it to IDE (the default is AHCI these days) he was able to boot. Again, no real problems. He just found a MS KB article about it, fixed the problem in Windows rebooted, set the SATA setting back to AHCI, and is now running just fine.
I'm not necessarily saying anyone should do it, but my experience is that you certainly could do it. No special prep other than backups were done. I didn't even get the chance to do a backup when my motherboard died, but I have a backup drive with daily backups in any case.
It just goes to show how very robust Windows 7 is. No blue screens. No hang ups. No flakiness. After all that Windows 7 can handle it. In fact I'm here and noticed this thread after a long hiatus because I came looking to see how many had experience with GPT and UEFI installs, but I'll save more of that for another thread. If I do a clean install it will be for that reason, not because I have to because of the major hardware change. BTW activation was a breeze. Of course the last time I activated this copy of Win 7 was nearly two years ago.
Before I forget, we are both running Professional. I'm 64 bit and he's sticking with 32 bit.
Now, I'm not recommending this. It may not work for you. If you try it and it doesn't work, don't blame me. I only have two data points here so proceed with caution. And always make sure you have current backups.