"File could not be found. Check the spelling of the file name, and verify that the file location is correct."... and because I've open the file by double click I was pretty sure file exists. BTW Notepad was able to open it. So what's the hell? The only idea what could be wrong was the absolute path length to the file. So I tried what is the maximum file path and I was surprised it is just 213 characters!!!
It's good to know, isn't it?