There is a watch type battery on your mobo, it prvides power to the bios to maintain it setting and keep the system clock acuract. Just turn off your computer, remove the battery, goto any place that sells watch batteries or your local computer storehand them the battery and tell them you need a new one. Then just reverse those steps. You will have to reset the system clock and you "might" have to re-flash your bios. Usually you don't have to but I just wanted to give that heads up so there are no supprises.
As far as side effects, it can cause problems with any program or service that needs the system clock. Other than that it will just drive you nuts, usually. But it can cause you problems with the bios. It is really not worth it. Just change the battery, and be happy! If you need any more help just let me know.