It sounds to me like the PC was already on the verge of dying when it was brought in. Perhaps they thought upgrading to W8.1 would solve this problem.
Ask the customer if they had issues such as NO VIDEO already.
Your Vista/7 comment is confusing:
You say the motherboard is only "rated" for Vista. You then say he has Windows 7 and that he'll have to keep that because you can't upgrade to Windows 8?
Anyway, I'm not sure what you expect me to tell you since you do work in a REPAIR SHOP.
Hey, just because I work in a repair shop, does not mean I have all the answers. Way to be rude.
Anyway, I've had a few people suggest that possibility to me already. I hope this isn't the case, and he isn't trying to pull a fast one.
It's rated for Vista (only has driver downloads to Vista 64 and not past that). Here's the documentation if you want a reference.http://www.ecs.com.tw/ECSWebSite/Product/Product_Detail.aspx?DetailID=805&MenuID=16&LanID=0http://download.ecs.com.tw/dlfileecs/manual/mb/eng/p4/G33T-M2_manual.PDF
He says he has Windows 7 on the machine. I suppose it could be possible that the motherboard can be used for Windows 7, but I'm pretty sure it's a bad idea going further to 8. Other than that, I'm asking him if he's had issues with the machine before.