Try cleaning out all of your temp and cache files and defrag your hard drive. Check your power settings - if its set for power-saver or blend, reset it to performance.
If none of that helps, back up all of your files on an external hard drive and do a clean install of your OS. Over time, your system collects a lot of crap (plug-ins, temp files, application add-ons, etc.) that you need to periodically clear out.