Time machine cannot be turn on because it cannot find a location for backups (including Macintosh HD)

Hi there,

My time machine cannot be open nor backup because it cannot find the backup location, which usually I select my local disk "macintosh HD" but this time it dispeared after I click "select backup disk".

I have tried to update my time machine application by installing time machine and airport updates, but it cannot be installed because the update requires Mac OS X 10.5.2 or newer, however, my mac uses 10.6.8 version. BTW, my AirPort losses connection frequently, usually it happens after the screen saver active and I have to reconnect to a Wifi by turning it off and on.

Any suggestion about my problem?

Thanks.