I have three hard drivers in my system, one WD 160G ATA100, Maxtor 40G ATA133 and Maxtor 80G ATA133, my motherboard is MSI645dx sis645dx with radeon 9000 pro.
After I install ati 4.1, my 80G harddisk became PIO4.
WD and 40G are still ATA100 and ATA133.
My system is very slow now.