Most hardware was not powerful enough for Vista when it was released. It's the pressed who killed it. Windows 7 received glamorous reviews. However, in hindsight, Vista and 7 are not all that different. Most of the changes that daily users would encounter are cosmetic.

Windows Phone

Microsofts primary problem was that it was late and (as one of the consequences) there are not that many Windows Phone apps. However, WP7 and WP8 were generally quite well-received by the media. Windows Phone is really a nice phone OS, what Microsoft f*cked up is the transition from WP7 to WP8.

And even if many changes between vista and 7 were "cosmetic", that's how people interact with their PCs, and things like having different UI styles all over the place is a huge dealbreaker that puts people off using it. (See also: Windows 8).

But Microsoft gave them the gun by agreeing to the OEMs' demand to create a "Vista Capable" classification, for machines that were too underpowered to run Vista well (see http://www.crn.com/slide-shows/channel-programs/206905984/tr...).

The OEMs didn't care about customer experience, they just wanted a "Vista!" sticker they could slap on as many machines as possible. MS had to know these machines would make Vista look bad; they should have resisted the demand. But they didn't, so tons of people bought machines they thought would run Vista acceptably, only to find out they did not. So they (understandably) thought Vista was just a dog that couldn't run well even on "Vista certified" hardware.