Have an old laptop? Before you throw it away, consider upgrading the hard drive to breathe some new life into that aging machine!
Here's a very quick way to significantly boost performance on your old laptop: upgrade to an SSD (solid state drive). Chances are, your laptop has a traditional spinning hard drive. Maybe you can even hear it when it's "thinking." Upgrading to an SSD can result in a significant performance boost, especially if you get an SSD made by a reputable company. Avoid getting an SSD on eBay from a no-name company.
If your laptop is really old, then you're probably going to need a 2.5" hard drive with an IDE or PATA connector. If you purchased your laptop within the last 3-4 years or so, then it probably uses a SATA connector.
I recently upgraded a few different laptop hard drives to an SSD and found amazing performance improvements ranging from quick start-up boot times and very efficient multi-tasking. You can now get decent SSDs for laptops for less than $150. You can get away with a 128 GB drive if you're running Windows XP, Vista, or 7.