i have an asus a7v133 with an ibm 60gxp attached to the promise controller and boot in 53 seconds. before i had a maxtor diamondmax plus 40 and it booted in 65 secs, so the hard drives makes a big difference. also the promise controller is much faster than the via ide controller; it takes off about 10 seconds of the booting time. you can move the hard disk to the promise controller after installing the drivers without a problem.
however, most of the boot time is caused by third party utilities, like a virusscanner, icq, seti@home and others. on my system the computer switches to the set resolution after 15 sec, then after about 10 secs extra windows has finished loading; the additional 18 secs are from the installed utilities.
if your dhcp server is fast it wouldn't make a difference; try setting your ip address fixed (and dns, etc) to see if it makes a difference. if it doesn't make sure you go back to automatically obtaining your ip.