Noise on the audio is a very common problem with laptops, especially cheaper ones. Aside from the power supply problems discussed here, some are just made with cheap audio chipsets and pick up all kinds of stray noise from the electronics and whatever EMI may wander in. For "professional" use, a Firewire audio interface or similar is usually used.
For casual use, a USB headset should do the trick... If you've got a headset that you're absolutely married to, you can also get a USB adapter on eBay or elsewhere, though cost often has an impact on your audio quality (though EMI is usually not a problem).
