Every time you open a new window in Windows Explorer, it searches the network for networked folders and printers. If you're on a network, great. But if you're just using your computer at home and you don't have any networked printers or folders, this search will delay the opening of new windows. So an easy way to speed up the start of Windows Explorer is to turn this off.

To turn it off start Windows Explorer and then go to Tools -> Folder Options.... Select the View tab and then uncheck the box next to Automatically search for network folders and printers which should be the first row in the list of options. Once unchecked, click the OK button to save your change.