It's probably due to no drivers available. I've seen an old s939 board get updated to Windows 7, but had to have a SATA expansion card installed because there were no drivers available for the old onboard SATA controller.
oh the model is an ACER em61sm/em61pm which is a modified foxxcon motherboard from what i've found out. and on Acer's website for the drivers it only goes upto windows vista ulimate 64bit (is vista really that bad? becuase if i cant get windows 7 would you recommend me stay with xp or vista?)
I have never quire understood the desire to put a new MS OS on hardware that has a older operating system. In the course of history, this has never resulted in anything else but a slower system. When we started out with Win95 being 40% slower than W4WGs on the same hardware, that shoulda taught us a lesson.
And before anyone calls Win 7 the exception, the reality is Win 7 should rightly be called Vista SP-3
I'd leave well enough a lone and put that OS upgrade money in a "new hardware" jar.
The bottom line is that generic drivers are available from multiple sources to support your mobo with Win 7. Just because the mobo vendor hasn't provided drivers doesn't mean they don't exist. In all likelihood, Win 7's stock drivers will handle most of your needs right out of the box.
In fact, most power users don't use mobo vendor provided drivers on their rigs. They use the generic drivers directly from the source (intel.com, nvidia.com, ati.com, realtek.com.tw, etc.....).
Download and run the Windows 7 Upgrade Advisor. It should give you a better idea of what will work with Windows 7 and what won't.
My best guess is that if Vista 64 drivers are available, then Windows 7 should work as most drivers are the same for Vista and 7. What is the chipset for your motherboard? nForce 430? nForce 400??
In my particular example in which there were no SATA drivers available for a s939 motherboard: the chipset was made by ULi, which no longer is in business so that's why no drivers.
FYI... I just checked the Nvidia website and it does have Windows 7 drivers available for nForce 430/GeForce 6150
The upgrade advisor for Windows 7 DOES NOT check your motherboard too, I only found that out by chance, you have to search for compatible MB's on the MS website, older MB's cannot run windows 7 and even more modern ones can't take advantage of features like Bitlocker either.
While I'm here, the systems I wanted to upgrade to Win 7 but couldn't due to the MB's, those I am putting new hard drives into as the drives have had it, my choices are to put XP Pro back on or Vista Ultimate, both 32 bit, reading the comparisons some are way old now so what is best with all the updates, XP Pro or Vista Ultimate??