I've had this same issue with older Dell notebooks & one PC. Installing a new CMOS battery fixed the issue.
Once these eventually dies, the settings won't be retained, including the hardware clock. Here is the removal procedure, on page 91 (2-61), PDF Reader required.
From what I can find, it seems to be the common CR2032 battery, available at may retailers, such as WalMart (best pricing) or pharmacies where batteries are stocked. These are also likely available at Radio Shack, but may cost more. WalMart has them in packs of 2 for less than $5. It may be best to remove & verify before purchase.
The real work here is getting to the battery, the few sources I've found indicates that a teardown is needed. If so & you wish to proceed, it would be best to take this time to clean up the internal of the notebook really good. This includes the cleaning of the heatsink & CPU surface & re-applying a thin amount of quality thermal paste.
Normally I wouldn't suggest this over a CMOS battery replacement, but since it's going to be apart anyway, may as well do so. It will run much cooler upon doing so, prolonging the life of it by possibly several years. Dust causes heat buildup & retention, acting as an insulator & is the eventual destroyer of many electronic devices, including computers, notebooks more so than tower PC's, due to the cramped space.
Edited by cat1092, 07 June 2014 - 01:19 PM.