"CMOS checksum failure" I was working on this customers PC today (for the third time). He bought this computer for $50 off some college kid. I put in a video card for him and setup the Internet on his computer. It is a 350mhz K6 with a PCChips motherboard. I swear I hate older computers. The mouse is a serial mouse and the computer was built by whoever with a serial connection installed installed on one of the brackets that is connected to the motherboard via a cable (notice I'm not sure what you call this thing lol -- wasn't working on PC's back when 350mhz processors came out). I checked this and plugged the mouse into the COM1 set of pins on the motherboard and also tried the COM2 pins. After rebooting on both spots the mouse still did not work. I had the other Tech guy take a look at the PC and I rebooted after he said COM1 should work and now I am getting the message: "CMOS checksum failure" or something very similiar (eh.. forgot the EXACT message). Well I replaced that battery with an exact duplicate that we happened to have laying around (the numbers matched and everything). That didn't work either, so I told the guy (owner of the PC) to go to Radio Shack and see if they had any. If this doesn't work, I'm going to be a bit upset.. I had a bad day as it is. hehe dangit!! Anyway, in the case that the new battery doesn't work what do I do? Also... any idea why the mouse is not working? It was working the other day.