Extremetech reports that "Microsoft partners apparently had a reference design for tablet hardware ready in time for Windows 7." They reportedly came to Microsoft with a request to support the hardware. According to Extremetech, the recently fired Windows president Steven Sinofsky refused to support to add tablet support in Windows 7.
There was no information how the tablet reference design looked like and there is at least some doubt that a tablet could have succeeded with the "old", non-touch-optimized Windows UI. However, if the report is accurate, it appears that hardware makers came up with the idea for a tablet substantially earlier than Microsoft did. Windows 7 was released in October 2009. Of course, if the report is accurate, it is also possible that Microsoft completely screwed its partners by first denying support and then releasing its own Surface RT tablet.
Sinofsky was also rumored to have been critical to killing the dual-screen Courier tablet in 2010, which, however, may have been a good decision and eventually sparked the ideas that ended up in Surface. This tablet is quite possibly the most emotional and anticipated product Microsoft has released since the Xbox 360, but Microsoft's slow adoption of touch computing - initial Windows notebook touch screen designs emerged as early as 1998 - and the following aggressive move to turn every Windows device into a system that prefers touch input could backfire twice. Not only is Microsoft late, but it may also have to fix Windows 8 for PCs.