Several common culprits in my view. (disclaimer - I am not a pro - so I may botch a term or two along the way)
Buffer size. Windows does not actually multitask, but switches between running processes very quickly. If you have your buffer size set too small - say 64, and your computer is slow, then you will hear a drop out (pops, clicks) as Windows moves on to the next process before completely writing that 64k buffer to disk. Setting buffer size to larger numbers is where I would start.
Latency. This setting plays right along with the buffer size. Some systems work fine at very low latency values (less than 10 or even 5 ms.) If you are recording audio or using software synths, then you may find latencies as high as 40ms are not noticeable to you. We all have different sensitivity levels, and of course what we are playing matters a lot too. In the end however, too low a value here will cause pops & clicks and may crash your software. You can experiment with increasing buffer size to 128 and increase latency to 20ms and see what happens. Just understand that both can work together.
Clipping. One poster noted too high a recording value (too loud). In the digital world, zero is wide open - full loud. There is very little tolerance for going above zero. That awful noise you hear are big-time digital artifacts crashing around. If you produce clipping while you are recording, then stop and reduce input volume and start over. If you are clipping only during playback, then you are over-running your sound reinforcement system (speakers, amps, that sort of thing). turn it down.
Bob
