Here is a link to the ASUS P3V4x manual. It doesn't show the settings for a 1ghz processor but as I understand it you set the fsb to 133 and multiplier to 7.5 to get your 1ghz. You might be able to ust the jumperfree mode. You will need to update your bios to v1006.
http://dlsvr03.asus.com/pub/ASUS/mb/slot1/pro133a/p3v4x/p3v4x-102.pdf