A sucker buys a new PC at the first signs of a slowdown. A savvy power user gives his aged PC a fighting chance for redemption. From tweaking your OS to compressing files to overclocking your videocard or CPU, there are plenty of ways to tune up a computer, and none require a trip to Bob’s House of New PCs. Follow along this step-by-step as we show you 21 of our favorite techniques for making a PC better, stronger, and faster — for free. These essential tweaks and tune-ups range from common-sense caretaking measures to practical adjustments that you'd be...