The previews of these operating systems were not launched at the same time of year; the first Windows 7 preview was seven weeks earlier in the year than that of Windows 8. However it is still interesting to see the time comparison graph, even considering the one and a half month head start for Windows 7.
If the time line was adjusted to give both release previews a coinciding start date, then at four months after preview availability Windows 7 was three times more popular than Windows 8. Also is you look at the graph it doesn’t look like Windows 8 is catching up, the graph shows a divergence unfavourable to Windows 8.
Source: Hexus