Any Time Start Application That Requires A Moderate Amount Of Processing / Whole Computer Skips

Any time I start an application that requires a moderate amount of processing, the whole computer skips. By skips, I mean the audio glitches and makes an annoying sound, the video freezes for a fraction of a second before catching up, etc. I was working on a video editing project last night, for instance, and this problem got really bad then. Now it happens whenever I try to play music through iTunes, or even a video online. So far, I have tried updating video card drivers, checking for updated chipset drivers, checking for possible overheating - nothing has helped. The Computer: I just bought the base components for this computer and received them in the mail less than a week ago. I put it together one night last week, and I noticed this issue as soon as I imported my music and got some working speakers attached. (It's much more noticeable with audio) [code]