If you're tired of the Windows supplied defrag tool there is a freeware (actually nagware) version of Diskeeper for download:
http://www.webattack.com/get/dkeeperlite.shtml
It doesn't have all the features of the full version of Diskeeper but it works very well. You can only defrag one volume/disk at a time and you must do it manually (as opposed to the full featured "set and forget"). Each time you open the program you will get a splash screen begging you to buy the full version. Not really much of annoyance given how often you will defrag.