Ok, so I ended up reinstalling Windows XP on my system with my Compaq QuickRestore CD's. The install didn't reset my computer to the factory presets though. None of the bundled software was installed. And, my internet is still acting strange. Some pages load very quickly, while others just hang, or give me error pages. Is it possible the during the reinstall, certain drivers weren't installed? or does this sound more like a hardware problem, maybe with my network card or hard drive?
I've already done what I can to test my DSL connection, and my ISP says there's nothing wrong with it. I've tested it on dslreports.com and it confirmed that my speeds are excellent. Downloading & uploading are as fast as ever.