To watch starcraft II beta replays just follow these instructions:
1. Get the game client and install it, you can get it from other torrents or from Fileshack and its completely legal.
2. Extract this rar to:
"C:UsersYOUR USERNAME HEREAppDataLocalBlizzard EntertainmentBattle.net
(merge maps but no need to write over files.)
3. Now to watch a replay double click it, select "chose standard program", then pick "browse", go to "C:Program FilesStarCraft II BetaStarCraft II.exe" and chose that file.

Done, now every time you double click a starcraft II replay you will automatically watch it in SCII without hacking the files! Note that this also works with all replays unlike the hacks.