I have an old pentium 133MHz and the BIOS /CMOS battery just died. I have replaced these before but this one is different. The ones that I replaced were circular watch battery type ones. There is nothing like that on this motherboard. There is a rectangular thing on it that says real time clock but is that the battery and if so how do I change it? I am an experianced computer person but when it comes to the older ones sometimes I get lost. Thanks for any help.