TechwareLabs has published a guide to performing house cleaning on your PC.

Just like your house needs cleaning on a regular basis so does your PC. Most users completely overlook cleanup of their PC. Now we are not talking about disassembly of your tower or laptop to clean the hardware, in this guide we are speaking about housecleaning of the operating system. Following a regular cleanup of your PC has proven beneficial effects on productivity and long term usability of your computer. If you are anything like me your desktop looks like a cluttered mess of files and folders. You may not even know what some of these files are or what they belong to. We are going to help you cleanup this mess and get your PC working smoothly again. Together we are going to take a peek under the hood of your OS and cleanup the mess that Windows leaves behind during normal operation.

A Windows Cleanup Guide