Quicksilver Installation Problems...

I dont know if im missing something really obvious here, but ive just downloaded quicksilver, however when i double click the downloaded file a progress bar flashes up for about half a second (i took a screenshot so i could read it and the title of the window is 'Archive Utility' if that helps)...the file extension is .bz2 , im fairly new to macs and im unfamiliar with this file type so i dont know if theres anything i need to do to it before i open it....i tried putting it into stuffit but nothing happened there...so any help appreciated ...

solved...just had to rename the file and remove the .bz2 extension and it worked fine