Where was i wrong???

I have setup and assembled an Intel P4 Orignal M/B built in sound and VGA, with all requirements, the pc boots up fine but in the device manager i see a yellow exclamation mark, it saya PCI device unknown. The PCI modem is detected but it is not recognized as a modem rather it assumes it to be a pci device and when asks for the driver it does not accept the modem driver. Please help