7200RPM is absolutely necessary to be rid of that bottleneck, first and foremost. A 5400RPM imposes a practical limit to the minimum size of the buffer, and from experience this can be as big as 256 (meaning anything lower you get xruns regardless of how good your audio interface is). WD has a 320GB 7200 mobile disk going for around 100 bucks. Secondly, the CPU. This is important because the lower the latency, the harder the CPU works. As such, if the headroom is not big enough, you find that even a little bit more CPU usage deals a heavy blow. I'd recommend at least a 1.8GHz Core 2 Duo, which is pretty standard these days. Overheating is an inherent hardware problem that comes with age. I bet your battery capacity has decreased as well. And a 7200RPM disk will output more heat, so get a flatbed cooler if the laptop's underside design isn't good enough to compensate.

2009/9/13 david <gnome(a)hawaii.rr.com> * And don't forget to report back the result so we can conclude it as true :) * Yes, SATA only. So beware. * Especially dust! If you can get those air pressure cans, they do the job mighty well. If not, battery-powered vacuum. But wait, how would you upgrade your CPU? If the processor in this laptop, like most others, comes as a "module" whereby the CPU and GPU are soldered on, it's definitely going to take more than 300 and may just warrant a new purchase in the end.

2009/9/13 Atte Andre Jensen <atte.jensen(a)gmail.com> Ahh..I must have been seeing things.