Switching to a solid state drive, as we've mentioned repeatedly, is one of the best upgrades you can make. Because of the cost, however, upgrading to an SSD usually means reducing your storage capacity. For the best of both worlds (speed and large storage), install an mSATA SSD as the boot drive to your laptop.
In essence, you're creating your own hybrid drive, with the mSATA SSD significantly improving your PC's startup time, application launching and file transfer speeds, and your current HDD offering all the space you need for your files.
Not all laptops support mSATA, but Laptop Magazine says that several models from 2011 and on do, including most Dell and Lenovo laptops. (Check your service manual or this compatibility list on My Digital Discount.)
Adding an mSATA involves a number of steps beyond just inserting it into the laptop's empty PCIe slot, so head over to Laptop Magazine below for the full step-by-step instructions for cloning your current drive, changing the boot drive, editing the registry and so on. As always, make sure you fully back up your system first. Enjoy the great speed bump without sacrificing space!
(If your laptop doesn't support mSATA, don't worry. There are ways you can survive on a small SSD.)
Triple Your Speed: How to Install an mSATA SSD Boot Drive in Your Laptop [Laptop Magazine]