You probably downloaded the Flat Files version. You want the one with "setup" in the name. I'll paste the link here, but if it changes - select the "Download" tab above and choose the download with the word "setup" in it (in this case, PAL_Setup_v2.7.5_x64.zip).
http://pal.codeplex.com/downloads/get/1504713
Thanks,
Bruce
http://pal.codeplex.com/downloads/get/1504713
Thanks,
Bruce