Computer won’t boot

PIII COMPUTER
450 MHZ
1 CR/W
1 CDROM
1 FDD
1 HDD

THE COMPUTER WON’T START, SOMETIMES IT WOULD TAKE 1 AND A HALF BEFORE I CAN GET A SCREEN AT BOOTUP. WHAT IS THE PROBLEM? ALSO THE CD/RW AND CDROM LIGHTS DURING STARTUP KEEP FLASHING SEQUENTIALLY? THEY WONT OPEN ALL THE WAY