Dunno if these are in any way related to your dilemma, but when I had similar disk drive symptoms (100 percent CPU usage and slow performance), it was because I had used 40-conductor IDE cables instead of the new 80-conductor cables when installing the disk drives.

However you say the drives are 133mhz, does that mean you're using the newfangled "serial" cables to connect the drives instead of the IDE cables?

Another thing to check is to make sure the "DMA" check box is enabled on the drives in the Windows Device Manager.