Start up form the basics
Remove all the PCI cards. Power up the system wiht just the CPU, video and memory. If all goes to the seek for the bootable drive, your basic puter is good, i.e., mobo, memory, power supply and video. Next, power it up with the hard drive and add components as you go. Sounds to me like you have a hardware conflict in your peripheral stuff. You may want to remove the hd and save your data in another system using your current drive set as a slave and then reformat andd re-intall windows. Have fun!!