Choosing Monitors

Hello, I have an older desktop and on the dell sticker, which  has the product key number it says.

Windows XP Media Center Edition 2005

NOTE: This is a huge tower (desktop). It stands 18 inches tall 7 and a half inches wide, the main color is silver, not that it matters; it's just I want to be as accurate as possible. If one needs any more information, (product key, etc..) please let me know.

Question:

Is there a particular monitor I need? For instance, I purchased a flat screen TV and was told that I could hook my computer to it, and use it as a monitor if needed. However, after trying to do this several times I failed. The only reason I can come up with, is maybe my computer is too old (2005) for it to work in a newer television. Do I have to find a 2005 dell monitor? Or, can a newer flat screen monitor work, if it's only a monitor?

All the best