Six years after its long-delayed but well-publicized release, Windows Vista now accounts for less than 6% of all Windows machines, a metrics company said earlier this month.

According to Net Applications, Vista's usage share of all Windows PCs in January was 5.7%. That's less than a third of the share Vista enjoyed at its peak in the fall of 2009—about the time its successor debuted—when it had a 20.3% share of all Windows machines.

By comparison, the even-older Windows XP held a 43.1% share of all Windows systems in January, or more than seven times Vista's share.

Since its 2009 peak, Vista has been shedding share, dropping 5.6 percentage points in 2010, 4.1 points in 2011, and 2.7 points in 2012. Presumably, most if not all of those Vista machines were replaced by ones running Windows 7, or the OS itself was upgraded to the 2009 edition.

In January, Windows 7 accounted for 48.5% of all Windows systems.

Windows Vista peaked in Oct. 2009 at nearly 21% of all Windows PCs, but has since slipped to under 6%.