Bios upgrade?

I have an old m81-x Delta mobo running with a pentium III 500 mHz and 384 ram. I originally had windows 98 SE installed when I bought it in 2000 but have recently replaced the hard drive and did a clean install of windows xp professional. Also, I added an extra 256 ram stick to the original 128 ram the system had back in 2000 thus making it a 384 ram system. My problem is that the system tells me that I have 640 ram, the board only has two dimm slots and the system reads four with 256 ram on one and 128 ram for the remaining three; Also, the system drags to process the information and, at shut down, I have to press and hold the power button to shut it down because I get the "It is now safe to turn off your computer" message. I went over to a local computer repair place and the gentleman working there told me that I had to flash (upgrade) my bios. Is this true? and if so where can I get the latest bios for this m81-x Delta mobo. I've been looking for the manufacturers site but I guess they're out of business. Do you know where I can get the latest bios upgrade for my m81-x Delta mobo?