The two most common upgrades we do to servers and workstations is adding as much memory as you can afford, and replacing your Mechanical Hard Drive with a newer and much faster Solid State Drive.
What may have seemed like a lot of memory at the time you bought your computer has gradually slipped below today's minimum recommend specifications. The speed of your computer is highly dependent on having enough memory. These days, having 4 GB of memory is average, and 8 GB is needed to make the newer versions of Windows run well. Every update that is pushed out by Microsoft, seems to put more and more demand on the limited resources of your computer. Windows XP, with all its updates, is an entirely different animal than what you started out with.
Solid state drives have come of age in terms of size, reliability, and affordability. Solid State Drives, or SSD's run about eight times faster than your existing drive, so everything you do wll run faster. We have the ability to upgrade your drive, without the need to reload your programs and data. Solid State Drives are also much more reliable than the older "mechanical" hard drives.