Here you go:
http://appldnld.apple.com.edgesuite.net/content.info.apple.com/iPhone/061-4955.20080710.bgt53/iPhone1,2_2.0_5A347_Restore.ipsw
This is a direct download link, make sure ".ipsw" is the only suffix, you may have to delete a ".zip" in the file name, depending on how your browser is set to handle downloaded files.
After you have the download, launch iTunes 7.7 and hold down the "option" button and then press "Check for Updates" in iTunes and select the new .ipsw file.
It takes 10 minutes or so to update - make sure to do a synch before the update!
Good luck!