If you check the contents of the C:\Windows and the C:\Windows\System folders, you will find many of useless DLL files. To save your hard disk space, use Windows Explorer to know whether a .DLL file still needed or not. To do so, right click a DLL file and then select Quick View. You will see some information, such as the applications that use it. If the application is no longer exist then you can safely remove it from your disk. Of course, you must very careful while doing this. You can move it first to other folders and then delete it several days later if there is no problem generated. N otice that if you can't see the Quick View option that means you must install it first from Windows Installation CD.
