I have a 720p HDTV and I have my PS3 connected to it (via component cables) with the res setting at 720p. When I change the PS3 output setting to 1080p, all I get is a black screen, but when I set it to 1080i I notice a more detailed difference, which is good and all, but I would notice that when I turn my TV off, that there are some lines on the screen where there are lines on my wallpaper that I use on my PS3. Is this harming my TV?

Also, my TV has an HDMI input, now I thought HDMI was only available for 1080p or 1080i TVs. So instead of using the component cables, would HDMI be necessary for my 720p TV?

First of all, are you using a Plasma or and LCD? If you are using Plasma DO NOT USE IT FOR GAMING. Because you will get screen burn which is what I think you are already seeing . and even for 720P HDMI >>>> Component cables, believe me.

Thanks Hot Rod

I'm using LCD btw, so would there be a real "big" difference if I went with HDMI? I just don't want to put down $60-100 on a cable.

YES

And if you do a bit of searching online, you can find find HDMI cables at a decent price. There is really no difference between low and high priced HDMI cables since data is transmitted differently than component cables. And one cable for all connections rules the school.

This is true. HDMI cables have gone down considerably in price.