By default, Vista's Disk Defragmenter runs automatically and periodically
in the background. As for cleaning up clutter, it's up to yourself how
much you want to do. Take a look at the options in Control Panel >
Internet Options.
http://windowshelp.microsoft.com/Windows/en-US/Help/1d862c06-aeb3-403a-8b58-2a76c8c676911033.mspx
A dedicated clean up tool will do a better job at removing old logs, temp
and index files from your system, but if by "other unnecessary things in
Vista" you mean orphaned registry entries and so on, I suggest you leave
it alone. Take a look at some of the earlier threads in this ng regarding
the subject.
http://windowshelp.microsoft.com/co...0E65F352DD13&lang=en&cr=US&sloc=en-us&m=1&p=1
Charlie42