that sucks. hopefully you managed to back it all up. next time also set it to just not even check for updates, just do nothing. does seem a bit strange that it changed on its own however, so it's possible a bug was in there (there are known viruses that fake a windows update to screw you over). if it wasn't, then... yeah, weird and still sucks.
still, i wouldn't say it's "shoddy quality" here - yes it has its problems but those problems come heavily from being popular and a billion parts being used. it's possible that the OS wasn't entirely at fault either, but something faulty inside the hardware/not enough juice in combination with the upgrade did it. too late to know what it was specifically NOW, but there are updates that just clash very, very badly with specific hardware and give problems like the one you had. regarding popularity though, apple users are finding out, the increase in popularity makes an increase in being targeted, with kaspersky outright saying they're a decade behind the times on security. now not wanting to move on to windows 8 is a whooole other story, but 7 should end up being like XP: still viable and reliable after almost a full decade.
linux basically becomes the only truly reliable one and with HP putting out a ubuntu laptop, steam saying they'll support it, and the rapid growth it's having, that OS may serve as a solid backup as security + reliability are the backbone of linux.
for the near future (as in, next 2-3 years) your options will basically be Windows 7, whatever macs are on, and ubuntu. the BEST answer to what you should do is dual boot your system - have ubuntu in one HDD, have windows 7 in another. then you'd be guarded against the problems you had now and if you choose to really leave windows you'd have a solid backup with massive support growing at a ridiculous pace. windows 8 is gonna be a weird mess that i'm still not sure what to think, but the changes scream that it's not gonna be as reliable as 7 is. macs meanwhile will remain as macs - consistent, but due to a bigger base, targeted a lot harder and apple's not fairing too well on that already.
edit: also before i forget, windows disks will forever confuse me in why we still need them. fact is there are... ways to fix your disk problem, especially so if you have the serial, since at that point you're doing what major retailers already do and probably is legal for a consumer to do too: have a standard copy of windows ready and you pay for just the code. literally that's how upgrade "disks" are done now too from guys like amazon, they just mail you a piece of paper with a serial on it and tell you to download it from microsoft. >_>;
the serial itself is the missing part. but it's the internet. you can figure that out.
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The King Wang.
Listen up Urinal Cake. I already have something that tells me if I'm too drunk when I pee on it: My friends. - Colbert.