Today I transformed my 2009 laptop into a machine that feels like it's from 2012.
All I did was rip out its 500GB spinning-rust hard drive from Seagate and popped in a 256GB Vertex 4 solid-state drive from OCZ. Now I'm kicking myself for not upgrading to an SSD a year ago.
If you're not up to speed on your PC components, here's the technical background on SSDs vs. HDs. For decades, hard drives handled storage chores by writing data as tiny magnetized patches on spinning platters. SSDs use flash memory chips instead, a design that can retrieve data much faster. The biggest drawback is the price: SSDs cost more and store less than hard drives.
My primary machine is a Retina-era MacBook Pro with a 256GB SSD, so I'm used to SSDs overall. What I hadn't appreciated was how much life an SSD can breathe into an older machine, in particular since processor performance isn't improving at the rate it once was.