Asus P5P800 MOBO - Slow to POST

I have 6 of these computers, 2 with XP SP1 installed, 4 with 2K SP4 installed. Every single one of them takes approximately 5 minutes to POST. Once Windows has begun loading up, everything flies. I cannot tell you which BIOS version they are running at the moment, as I cannot access the computers. They all have P4 530 (3.0 Ghz) CPUs, Asus V9520 video cards, and 1 GB (2x 512 sticks) Kingston DDR RAM.

As I don't any other RAM or CPU to swap out to troubleshoot, or the time to do so, I'm at a stand still.

Has anyone else encountered this problem? I've done some searching through ASUS's website, as well as some searches through google, and haven't come across much. Any thoughts would be apprecaited. Sorry if I didn't supply very much information for the time being. Tomorrow I will add more if I get a chance to take a look at them.