SourceTree for Windows does not fully honor git's gitignore pattern format. You can observe the problem by using the git shell for Windows side-by-side with Sourcetree.
See attached tree.PNG for the example folder structure.
See attached gitshell.PNG for how git shell for Windows sees the working directory. Note that I added all non-.gitignored files as seen by git shell using git status.
See attached sourcetree.PNG for how Sourcetree sees the working directory. Note the unstaged files that should be ignored if Sourcetree is behaving the same as git shell for Windows.
See attached .gitignore for the actual .gitignore file from the working directory.
Refer to the 'PATTERN FORMAT' section of http://git-scm.com/docs/gitignore. Specifically:
A leading ** followed by a slash means match in all directories. For example, **/foo matches file or directory foo anywhere.
A trailing /** matches everything inside. For example, abc/** matches all files inside directory abc, relative to the location of the .gitignore file, with infinite depth.
In this case, all of the unstaged files from sourcetree.PNG should be ignored under one or both of the rules above.