Please make sure to have all of the latest Windows updates, Java installed and updated, and scripting/activeX enabled on your web browsers. Pop-up/script blockers can also cause issues with the downloader/launcher.
If the download finished 100%, you should be able to do a file search for "DATA1.cab". In the same folder as that file there should be DATA2, DATA3, and a setup.exe file. If you have those 4 files there, then run the setup.exe to install the game.
If those 4 files are not there then the download did not complete. You will either have redownload the client or you can go to our main download page and use the direct links to the 4 files: http://allods.gpotato.com/?m=game&a=download