There's no Git for Windows 2.x

[tessiof]

On Windows systems, Git looks for the .gitconfig file in the $HOME directory (C:\Users$USER for most people). It also still looks for /etc/gitconfig, although it’s relative to the MSys root, which is wherever you decide to install Git on your Windows system when you run the installer. However, if you are using Git for Windows 2.x, it is C:\Documents and Settings\All Users\Application Data\Git\config on Windows XP, and it is C:\ProgramData\Git\config on Windows Vista and newer.

I'm pretty sure there's no Git for Windows 2.x, nor Windows 3.x, Windows 95, etc..
I assume the author was going for:

if you are using Git 2.x for Windows

In this case, since the book is about Git 2.0 onwards, a better way would be:

On Windows systems, Git looks for the .gitconfig file in the $HOME directory (C:\Users$USER for most people). It also still looks for C:\Documents and Settings\All Users\Application Data\Git\config on Windows XP, and C:\ProgramData\Git\config on Windows Vista and newer.

[i-give-up]

"Git for Windows 2.x" here means "version 2.x of Git for Windows".

Given the context, I doubt people would think that it's referring to an operating system, but I might be mistaken.

[ben]

Yeah, I doubt people will think Git was written for an OS that was released in 1987. 😀 I'd accept a PR that fixes the grammar, though.

[YueLinHo]

Git for Windows is a term. See: https://github.com/git-for-windows

Perhaps using Git for Windows 2.x (using `)? or GfW(Git for Windows) 2.x?

[ben]

No, I think we have enough acronyms. I think "version 2.x of Git for Windows" is the least-awkward-while-still-being-correct thing I can think of.