This is a good question, because the lessc path is dissimilar in many ways to normal installation paths on Windows. I was able to confirm that lessc does need to be added to your Windows environment variable called PATH in order to for sublime-less2css to work properly, and this is directly from the maintainer of the sublime-less2css module: https://github.com/timdouglas/sublime-less2css
- Open Control Panel
- type 'env' in the Control Panel Search Bar to bring up the 'Edit the system environment variables' option (select this option, then tell the User Account Control dialog to 'Continue')
- click the 'Environment Variables' button
- Go to the System Variables section --> click once on the line that says PATH --> click 'Edit'
Add the following to the end of the strings in the window that comes up:
;C:\Users\{add_your_Windows_username_here}\AppData\Roaming\npm
Since my Windows user name is cknoettg, mine looks like this:
;C:\Users\cknoettg\AppData\Roaming\npm
Finally, click OK --> OK --> OK
Now, retry the program.
Important proviso: For this solution to work, you must have installed less on your Windows machine using npm - the Node.js Package Manager. (Which you can get here: http://nodejs.org/)
If you used a different method to install lessc, the exact path to add to your environment variables is going to be different than what I have suggested. Let's say you installed 'lessc' directly in a folder called "C:\less\bin". In that instance, you would add:
;C:\less\bin
to your environment variable PATH.
Also: I noticed in the error message that you posted the following line:
less2css in C:\Users\myMachine\AppData\Roaming\Sublime Text 3\Installed Packages\Less2Css.sublime-package
It is possible that your Python file is hardcoded with the path C:\Users\myMachine\AppData\Roaming\Sublime Text 3\Installed Packages\Less2Css.sublime-package. IF that is the case, it is possible that your lessc program is in the path: C:\Users{insert_your_Windows_username_here}\AppData\Roaming\Sublime Text 3\Installed Packages\ .
IF this is true, then you will not only have to modify your Windows environment variable PATH with:
;C:\Users\{insert_your_Windows_username_here}\AppData\Roaming\Sublime Text 3\Installed Packages\
You will also have to manually edit your Python file by substituting the text 'myMachine' with your current Windows username on the machine that you are located on currently. You could even try just making this direct edit to the Python code without changing the Windows environment variable, but it may or may not work.
To see a way to run your program WITHOUT editing the environment variable, you can see here (although I don't recommend it for a variety of reasons, not the least of which is the additional typing involved each time you run your script): How to install and run lessc on top of node.js and Windows?
Good luck!