It is indeed the CMOS CR2032 battery. You may want to access the BIOS and make note of the BIOS settings prior to replacing the battery as most likely the BIOS settings will reset to default. This Dell support page will help. A 16 year old system still going strong, very impressive. The owner's manual has more information on the procedure at page 170 here.
I received a message saying my system battery was low. I have not checked it, but I think the battery is supposed to be a CR2032? If I remove and replace the battery, is there anything else I need to do? I use Vista. Thanks, Jerry 1/29/2023
XPS 420, system battery low