If openstudio.exe is in your PATH, then you can just do openstudio.exe run ....

To give the path to the OSW, either you give: * a full path (eg C:\path\to\compact.osw or perhaps C:/path/to/compact.osw), or, * a relative path given the current directory by using the ./ prefix ./path/to/compact.osw or omitting itpath/to/compact.osw.

If you pass /path/to/compact.osw it thinks of it as an absolute path (which would be valid on Unix, but not windows)