I also have an old laptop, but thankfully it was good when new so I'm getting buy. Wanted to let you know that I am headed out to buy the Behringer USB Audio Interface (U-Control UCA202), that is supposed to work as well as the external sound cards, but only cost about $30. Might bet you past needing a new sound card. Also, Creative makes a sound and video external box. For a few hundred, you could probably get all the processing you need without buying a new laptop - I assume you already have USB ports, Ethernet, a keyboard, monitor, etc?

Panny 3000 PJ, 118" Carada, Denon 3300, PS3, Axiom QS8, PSB 5T, B&W sub, levitating speaker wire