Hard to tell, but sounds like a problem with your laptop's mains power supply. If you search eBay/Amazon etc with your laptop make & model number you should find a new one for around £8-£15. Make sure it includes the mains cord & wallplug as some suppliers charge extra for this. Avoid the 'universal' charger many electric shops will offer - these cost £30+ use plug in adapters that wear out or get lost.
Rob
August 2010