PC clock stops working-help please

Hi ,
For some reason my clock on the task bar has stopped working- i have corrected it 3 times now and it works while the PC is on - but as soon as i switch it off it stops !??:?
This hasn't happened before -any ideas how to keep it working and why this has suddenly happened ?
Thanks a lot


There's a small battery on your motherboard, around the size of a copper penny (assuming this is a desktop) - this is what keeps track of time when the PC does not have power as well as your other basic settings. After time this battery can fail which means each time the PC loses power the clock will be reset.

Do you get any errors on startup? Normally when this happens you will see something like "CMOS CHECKSUM FAILED - DEFAULTS LOADED" when the machine goes through its power on self test (POST)


Sounds like the CMOS battery has gone.

Its easy to replace and looks like this (Assuming you're on a desktop!!):


Original Poster

Thanks for info -no i haven't had any error messages at all.
Where would i get one of these batterys from ?
Yes ,its a desktop.

They are standard lithium batteries - if you look at the existing one on your motherboard you should see a number prefixed by CR (such as CR1220 in the picture above), you need this to make sure you get the right one. I would think you'd be able to buy one from a supermarket, if not try someone like Dixons, Maplins etc.


They are quite cheap and are found in calculators etc to.

They are normally around £1.50-£3.

Let me know the number on the battery

I have some spare and may be able to dig one out for you.

Just had a quick look, Mines CR2032, So they do have different numbers (I've never had one fail!)

They can go after 4 or five years depending on how much you use your PC. I have an old laptop here and the cmos battery has just gone after 10 years.

Original Poster

Thanks everyone- i presume i will have to take the cover off the tower to find the battery number , if so will do that later tonight.
Thanks too Stora -lovely offer - will let you know the number later.


Thanks everyone- i presume i will have to take the cover off the tower to … Thanks everyone- i presume i will have to take the cover off the tower to find the battery number

Yeah, It'll look similar to the picture and probably be near one of the corners of the motherboard.

Original Poster

Thanks again for everyones help.
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