uninstall your anti-virus/firewall (if you have any)
get ccleaner
http://ccleaner.com/ (free)
check your startup processes under tools, delete everything that you don't recognize or use. then use the registry cleaner under issues
learn your programs/processes/addons/plugins, understand what does what, and you'll never need a anti-virus/adware/spyware again
and yeah.. defrag your hdd
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