Uninstall everything you don't use
No, really, everything; browser toolbars, programs you forgot about, games you didn't finish. See that system tray in the bottom right stuffed to the gills? Thin it down.
Be sensible - leave things like Windows updates and hardware drivers. If you're not sure what something is, grab a friendly geek or leave it alone.
While you could use Windows' in-built uninstaller, something like IObit Installer will allow you to somewhat automate the process by queuing a whole lot of uninstalls at once.
For most Mac apps (Microsoft Office and Adobe Creative Suite are notable exceptions), you can uninstall apps purely by dragging them from the Applications folder into the trash, and emptying it.
Credit: Craig Simms/CBSi