I'm afraid that the problem doesn't lie in the unlink: DeleteFile
succeeds. The problem is that the file is only marked for delete
until such time as the last SHARE_DELETE handle on it is closed.
Until that time, an attempt to (re)create the file for anything
other than SHARE_DELETE will fail. As you say, it's a timing
issue.

Making os.unlink on Windows more robust may be a good
idea, but it's not going to help this issue. See my test-case.py
on an earlier message for reproduction:

http://bugs.python.org/file16869

TJG