The easiest thing to change when clock loses time and other info is the battery on the motherboard.
Ensure computer is powered down and mains supply not switched on to the machine.
If it's software related cannot help always bypassed Vista.
Do the normal scans for Spyware and Viruses, if recently updated Windoze delete that update and see if it clears.
Last resort roll back to a earlier working time, or repair OS by running repair facility.
"My lovely car now sold onto a very happy new owner.
I still love this marque and I will still be around, preferred selling to breaking, as a great runner and performer"