Do some maintenance.
Keep it clean- Registry cleaner: Your registry holds all the information regarding updates, installs, uninstalls etc. so this needs to be cleaned. This will optimize and remove redundant or unwanted items.
Keep it clear- Delete any unused or unnecessary programs and files. These may be taking up space, memory and resources, thus slowing your computer. Also delete your cashe/ temp files, empty your recycle bin, clear your internet browsing history, etc.
Keep it organized- Defrag your hard drive. Fragmentation severely degrades the speed, performance and reliability of your computer. Try Diskeeper 2008, its automatic so you never have to worry about defragging anymore. You can download 30-day trial-ware at www.diskeeper.com
Keep it safe- Get a good Anti-virus/ Anti-spyware