The key to helping one's installation of windows from becoming slow and bloated is to attempt to take proper care in the deletion of old or useless files. These can appear in the form of unused DLL files in your system directory, temp directories overloaded with pointless entities, or even
items left over after you "thought" you uninstalled a program. All can muddle one's hard drive so as to cause severe amounts of drive fragmentation, as well as space to be lost.
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