I have the asus p7p55d evo m/b. i had 4 sata hard drives installed when i upgraded. i disconnected all the drives except the c drive. it set up perfectly. the problems came when i hooked up the other 3 hard drives, it comes up with a load issue requesting me to set up the bios or use a boot disc. i had this issue before with other m/b's but it has been a while since i built a new pc. i tried various confguratiosn from the bios and nothing works. disconnect all the other drives except the c drive and it works perfectly. this is set up with windows 7 and 64 bit mode.
I had the same problem with the P7P55D. Go to the BIOS setup page where you set up the boot devices and boot order. Right below that is a entry that says Hard Drives -- that's where you choose the HD that is in the boot devices list.