Many, (not all), but a good majority of Windows problems can be traced to the poor job computer makers do installing Windows. They load it up with junk, put little to no effort into drivers, and the results is a sub par experience. One of the best ways to avoid this is to buy computers that are Microsoft Signature Editions. These have been tuned by Microsoft and really do run better. You can buy them directly from Microsoft, from Amazon, or some computer makers. Sometimes they cost a little more, but the results are worth it. You can find more info here:
http://www.microsoftstore.com/store?...emeID=33363200
Another problem is AV suites. Can't tell you how many computers have seemingly unrelated issues such as crashes and hangs and performance problems that magically go away after uninstalling some of the monster AV suits out there. Having unexpected, hard to track down issues? Uninstall your security suite, make sure Windows Security Essentials (Windows Defender in Win 8.X) is active and test it for a week or so. The difference might amaze you.
Just some thoughts on my experiences after having worked on hundreds of PC's.