XP dropping HDD’s

Im built a P4 3.2 on a asus P4c800 deluxe mobo with 2 WD IDE 200Gb HDD. The HDD’s have 2 partitions on each(on IDE1). Master is C and D, slave is E and F. 50% of the time when it boots up it has all 4 HDD, the other 50% it only has the master C and D and E and F are not there. Any insight?