Not a lot of info to go on but , try starting from the beginning again . Remove all files from the card ( save the ones you want on the PC ) verify the cards size and resolution you are recording at. That will give an indication of how long you should be able to record for , I think I am right in saying that the 4 gives a countdown on the screen any way. Recharge the battery . Remove camera from the skeleton case and check record switch is free to operate and not sticking. Start it recording and leave it on the table or wherever it's not going to get disturbed and see what happens.
Ignore all that if it's new and take it back to wherever you bought it from and let them deal with it.