Toshiba laptop won't startup

I have a 5yr old Toshiba S1900 laptop which completely froze when I tried to shut it down. As a last resort I popped the battery out of the back to reboot it, but when I reinserted it, the computer won't turn on. It doesn't work on the mains without the battery and when the battery is in it (and it's plugged to the mains), the battery light is shown as orange (not green as it would be when it's charging). I'm trying to find out if it's more likely the battery is damaged or the hard drive before I spend a fortune on a new battery.