I'm far from an MC expert, but I do work in digital audio.
There is a program you might find helpful called DPC Latency Checker:
http://www.thesycon.de/deu/latency_check.shtmlIt will display latency in real time, a bit like an hospital EKG machine. The Y-axis is latency, measured in microseconds. It's designed for digital audio/video and will also supply a running commentary about how well your system will handle things.
Anyway, when the graph spikes, hopefully there will be some correlation with your audio drop outs. You can then experiment and try and find the source of the problem. Indeed, I would expect MC is not the problem, and certainly your processor speed is not, either. Sometimes, the cause is a fan, an optical drive, another USB or Firewire device; the networking (esp. a wireless connection)... Perhaps you could try an ASIO driver, as well, instead of your current driver, if your setup will support it. (I believe MC does have ASIO support.)
Hope that helps!