Try hitting the Change Calendar settings, Click on the date tab, then make sure the short date is 3/9/2009, long date in Monday, March 09, 2009. Make sure the format is M/d/yyyy. make sure first day of the week is Sunday
Click on the time tab and make sure the short time is (whatever your time is in this format: 2:48PM. Long date should look like this 2:48:57 PM.
Under Time Formats, short time should read h:mtt:
Long time should read h:mm:ss:tt
AM symbol is AM
PM symbol is PM
Also, check under Regional Options to check the formats are the same.
I have never heard of a clock stopping, in a running computer. Were it the bios battery, the clock would still start to run, albeit at the wrong time, whenever you powered up.
Have you had any third party programs installed which influence the Time/Date?
I would follow Reghakr suggestion, but do it through the Control Panel. Date and Time . Start with "Change time Zone", which will automatically set your m/dd format to that of your country. (Mine is the otherway around!) The "Change date and time" - Change calendar settings" Finally "Set date and Time. Cross your fingers and see what gives.