Date format keeps changing

Anyone know why my W2K system insists on reverting back to short date format MM/DD/YYYY. Each time I set to format DD/MM/YY under regional options the system will be fine for a few days but then change the date back to MM/DD/YYYY. Originally I was using an MSI KT7 motherboard and suspected the BIOS. Updating the BIOS didn’t cure the problem. Due to motherboard failure some months later it was replaced with a KT3. W2K was clean installed but the problem still occurs. The system in question is connected to NT4 domain and Netware 5.1. SP3 is applied and the current BIOS is up to date.