Nitpick: 1.5TB HD.
You have a fine video card. Changing it will make no difference for your needs. If you need clearer letters, you need to set the monitor/TV to its native resolution (which may or may not be 1920x1080--you'll have to check it yourself). LCDs are not like CRTs--they do not look good at lesser resolutions. Also, make sure to be using a digital connection (DVI, HDMI, or Displayport).
Then, in display settings, change the DPI to 150%. This will not only increase font and form sizes, but also scale up the displays on old applications. It makes the old ones fuzzy, but they do get bigger. Compatible applications will scale very nicely. If this works out well for you, note that with the custom option on the left, you can go up even higher.
Now, make sure to restart after that, whether it asks you to or not. Now, go personalize, windows color and appearance, then advanaced appearance settings. From there, you can adjust the fonts and other items used even further. IMO, Tahoma and Verdana tend to be the easiest to read in Windows w/ Cleartype.
Finally, go to display, and then adjust Cleartype. You may wish to go back and adjust it a few more times, later.
That's it for Windows. All the rest will need to be done in applications. For instance, if you use Firefox, there are addons to set the default zoom level. As someone with mild myopia, I would also highly advise finding fonts you like--I use Tahoma and Consolas (you have to go download it) on Windows, Dejavu Sans on Linux--and disable the ability for web pages to pick their own.
For special cases, Windows' own magnifier is not bad, and there are good freeware ones out there, too, if you want more control.
Finally, with all that, consider messing with your monitor's brightness, contrast, CCT, and gamma settings (if it has multiple gamma curves, try them all for a few hours). Getting good contrast between medium and dark, and medium and light, colors, can help a decent bit, but I would make this a very last step. That said, if you poke around your TV's color settings, and it has a real color standard preset (sRGB is the most common), go ahead and use that, before messing with the fonts and all, then fine tune it later. If it has only typical TV settings, make sure it's on whatever is the most normal/boring looking.
