SumatraPDF is excellent. Sumatra doesn't register itself with Win 7 on my computer. I tried to associate SumatraPDF with all supported file types but no success. It's very hard to do all the file types one by one. It will be great if there's a button to do it once for all. It will be a useful feature to overwrite other application as the default reader because many people want to replace other readers with SumatraPDF. Thank you very much.