This isn't much of a "Tweak" really but it allieviated the problem quite quickly for me, I now have no pops or crackles. It turned out that my Hard Drive was to blame for my sound crackle/skips. I recomend defragmenting first, if your sound still is messing up, try formating. For me I have to replace my hard drive completely to FIX the problem completely. Anything at 7200 RPM, with enough space for all your files will do, I personally recomend one with 8megs of cache as that seems to speed things up nicely. Good Luck!