I found the bug where it needs the lua extension when you're importing through a parent folder: my "return the file extension" function wasn't checking for the path separators as it walked backwards from the end of the filename, so it thought the imported file already had an extension and didn't append .lua. You'd get the same problem with any folder with a dot in its name.
But about the Windows problems: I suspect the problem is that pdc is expecting backslashes on Windows but we're using a UNIX style filesystem interface that handles forward slashes. That would explain why we haven't had a flood of complaints that our examples have the slashes backwards.. Here's a pdc.exe build with the path separator swapped:
pdc.exe.zip (224.1 KB)
If it's even possible to run it (I can't test it here, sorry!) can you check if it works better? Thanks!