Batteries for boards are commonly seen where large battery racks in consumer electronics, calculator sections are in retail dept. stores as well as where digital watches are sold. Different brands like Eveready and Duracell will see a different two letters added on front of the usual 2032 number.
For Duracell used here that would be DL 2032 while Energizer would be CR or CL 2032 the letters simply pointing at the brand. These are 3v lithium type coin sized batteries even found at Radio Shack and other small stores as well.
First verify the number or take the battery along with you if it shows something other then 2032 on it. There are also 2031 numbered 3v batteries and other numbers used as well. You want the exact match for it.
Good temps helps since that shows that you are not seeing an overheating problem with the cpu or board. You still could have a problem with the current video card however since you would need a different program or actually mount a sensor to see what those are at. PC Wizard found at CPU-Z's site will show card temps as well as others. CPUID
Putting that all aside it's also likely that the board itself has a problem. Sometimes a simple update of the bios will correct things if the board isn't seeing a bad cap or two acting up.
When trying a battery from another first see if both take the same number. The 2032 number is pretty much a standard now while some older models may have used a different one for a slight difference in voltage.
The old AMD Atholon XP3200+ took a pounding for sure. When the board itself was eating batteries and the cpu reached 85C and no longer would run with the fsb set to 200mhz in the bios it looked like the cpu backclocked itself. Later when simply tossing a new battery in XP3200+ not XP2500+ is what was then seen when setting it back to 200mhz again.
You can't rule anything out on older boards just to note. If you are seeing a bad cap or some other component failure you'll find out fast enough once a fresh battery is in. The battery is simply a lot cheaper to replace then going for a replacement board likely newer meaning new cpu. memory, video and sound cards, etc. in that sense.
The problem now is the battery was simply the low cost item to see replaced. On older systems it's common to see problems when a battery goes. Now you have to start taking a serious look at hardwares which include memory and the board itself as likely.
For seeing what card temps are PC Wizard 2008 will show that as well as cpu core, cpu, and board temps as well. Just like downloaders no software is ever 100% fool proof since even PC Wizrard, Everest Home Edition(formerly free version), and others can give false readings at time.
You have to get a can of cleaner right this minute! No standing around idle staring at walls! let's go!
That's showing you right there that regular cleaning serves two main purposes of 1) keeping temps down! 2) keeping buildup from seeing the loss of continuity in slots for memory, video cards, and other expansion devices.
Once you made the effort you are now suddenly noticing an improvement. You would be surprised at how many don't even do that much and wonder why things fail on them!
Someone known here was asked if he wanted to borrow a drive when he couldn't get Windows on a sata drive he bought at the time for a new build. Now step forward about 1 1/2yrs. when Windows problems of all types were being seen where he then asked for help.
Try pulling a blanket of dust off the main board where you pratically need a strong pair of pliers to see that done! The hard drive was obviously "well done"! from heat inside that case. Try a chef's worst nightmare! or lack of common sense!