I assume you are looking at the device manager window? Have you tried clicking on them and installing or finding the driver for that specific hardware?
Even with these alerts, does your system run fine? No other problems other than this alert?
Bingo! your mobo wouldn't know what to do without those Northbridge PCI bus drivers installed. Generally, your systems seems to run okay but if you started to load up those PCI slots you'd know why the drivers were needed!!!