After several weeks of working off my netbook, I've finally diagnosed with 100% certainty from where in my desktop were the crazy whirling grinding sounds coming. Apparently there is a 80mm fan in the front of the case behind (or in front?) of the hard drives. It seems that its ball bearings have either ground themselves to death or are in need of some lubrication. Either way, a new 80mm fan is 7 bucks, so I'll just get a new one. The front fan is currently unplugged and it's sooo much quieter now. I almost want to just forgo the fan entirely.
Anyway, I'm not back in business(!)... whatever that functionally means.