I think it can be done as follows.
first, you'll need a text editor that will not corrupt the Astrotortilla astrometry.net config file by converting the line endings to DOS-style. Avoid Notepad and WordPad. Notepad++ is a good free alternative, and there are numerous others.
C:\cygwin\etc\astrometry\backend.cfg in the text editor
(I'm assuming your Astrotortilla cygwin is in the default location,
- find the line that says:
and add a line below it that says
(replace YOUR_USERNAME with your Windows user name)
(the forum is splitting that into two lines, keep it as a single line in the file.)
- Save the file. Make sure your editor does not convert the file to DOS-style line endings.
- Run a plate solve in Astrotortilla. It should pick up the ansvr index files.