I can't get my TV working as a second monitor anymore..

So, I have an HDTV in my room, (a Sharp), and I used to be able to use it as a second monitor for my Gateway FX laptop using a standard video connection (the pre-DVI kind). I tried getting it hooked up when I started college again with an HDMI cord, and I have had no success. I've also tried the standard video cord again, and that didn't work either. Does anyone have any suggestions? My laptop picks up the monitor (I can drag windows to where the second screen should be), but the tv has no display.