Learn how to use your computer!
EDIT:
Here is what I use... all of them are free:
CCLeaner to delete old crap files.
Malwarebytes
Also, make sure to uninstall crap software and everything else you are not using. Use VMs for cracked softs as they will usually fuck up a lot of shit on your system.
u are using windows. They will always be slow after some time no matter what, it's how they work.
get some *nix system, ubuntu is easy to use