1) Download Revo Uninstaller and uninstall everything except drivers. (Note: Revo is free and also deletes crap from the registry when it uninstalls a program.) If you accidently uninstall the drivers, you can just go to hp.com and download only what you need. The computer will still run without the drivers, just some features will be absent.
2) Double your RAM. Go to www.newegg.com and make sure you have at least 4gb of RAM.
3) Remove the hard drive and install an SSD.
That's about all you can do, but the first option is free!