The intel chipset on your p4b266 can handle 8 pci irqs.
Try to free irq by disabling serial ports in the "I/O Device Configuration" section of your bios ( BTW: lates version flashed: ftp://ftp.asuscom.de/pub/ASUSCOM/BIOS/Socket_478/INTEL_Chipset/i845d/P4B266 )

You can try to assign the irq manualy for each pci slot in the bios. Set "Plug & Play O/S" to NO, or try YES. "Reset Configuration Data" => YES.

You didn't mention your Windows version. Is ACPI support installed?

Jason

: Helo Bill, thank you very much for replying. There isn't an option that specifically says USB 2.0, however there are options like "USB legacy Support" and "USB Function" which i've enabled already. I've read the manual thoroughly a few times, and checked the bios too quite a few times too. They seem to be the only options available. From the Systems Information within windows, i found that the USB 2.0 controller is sharing IRQ with the IEEE 1394 Controller. Would that be a problem?Thanks again for your help.: This will be a learning experience for the two of us. Have you looked in BIOS setup to be sure that the USB 2.0 ports are enabled? They are officially an "option" in the literature and are likely disabled (dumb).: Bill: : Hi, i have an ASUS p4B266 motherboard with built in USB 2.0. However, when i connect my devices to it such as the Microsoft Intellimouse 2.0, Logitech cordless freedom & Compaq Ipaq, the system will not detect their presence. The intellimouse wouldn't even power up (optical light doesn't turn on). Both the drivers supplied from the Asus driver cd and the one from asus website doesn't seem to have any effect. The manual said it shares the IRQ with PCI slot 1 and slot 5, but i haven't got any devices plugged in those particular slots. Unless AGP is counted as PCI slot 1.