Video Card Installation or Upgrade
Video card or graphic card will make a tremendous improvement in overall system performance. With a dedicated video card, your CPU will not work as hard, and you will have more RAM available to run programs, which will mean that your hard drive(s) are accessed less. This translates to programs open/close faster, and the display on your monitor gets refreshed faster. That is, after the program opens (or closes, or whatever), you will see the results faster. These improvements make the computer feel like a faster computer, even if it's not significantly faster.
Hard Drive Installation or Upgrade
Upgrade to larger or faster hard drive to increase speed and performance, or add an extra hard drive is your are running with low free space. The speed at which the PC boots up and programs load is directly related to hard disk speed. The hard disk's performance is also critical when multitasking is being used or when processing large amounts of data such as graphics work, editing sound and video, or working with database.