Most laptops have an extra, nearly always unused socket for Mini-PCle connections, either underneath the keyboard or the bottom flap. This space is sometimes used to add an extra mobile wireless connection, but if it's not in use, consider filling it with an mSATA format mini solid state drive so it can be used in parallel with the main hard drive.
Hooking up an SSD provides the option of storing operating systems and programmes on the speedy SSD drive, freeing up the hard drive to be a massive storage device only. Just remember, if you do put the operating system on the SSD, set it up as the main drive in the computer's BIOS first.