Problem with the screening of videos on TV

A few days ago I made a clean installation of windows 7 after I had windows XP before that. I got a LG TV and ATI hd4870 as graphic card.
I am not sure how to explain the problem in words also because I can't take pictures to demonstrate it but ill try my best.
My computer is connected in HDMI to my TV and now there is a problem that every time I play a video file on the TV the light gets mixed up, the picture's light goes brighter and darker all the time.
I am pretty sure the problem isn’t with software, the codecs or the TV itself for several reasons; 1. I didn’t have any problems with the exact same software and hardware on windows XP 2. When I play the same files on my computer's screen I don’t get this problem 3. I have a satellite connected to the same TV (also with HDMI) and I have no problems.
I also tried to install older versions of drivers for my graphic card and it didn’t help either.
All this leads me to conclude that the problem lies in windows 7.
Hope someone can help me sort it out.
Thanks a lot!

I am suggesting you an alternative method of watching movies rather than giving a solution to your problem with Windows 7 Computer.

Instead of using a computer to play movies on a HDTV, try using WDTV Live media player (a small hardware box, looks like a compact USB HDD from Western Digital with a remote control) with one or two usb HDDs (upto a max of 2TB) containing all the media (mp3s, movies, avi, mkv, mp4 etc, photos like JPGs etc...) connected to a HDTV by a HDMI cable. You will get full HD video with DTS passthrough, and an option to connect a Dolby 5.1 surround home theatre to get the best of everything.

There is a lot of difference in watching the movies on a HDTV in 1080i rather than watching movies on a computer connected to a TV.

I have been using this setup for the last two years (minus 5.1 surround home theatre) and very happy with the performance. You throw any file at WDTV and it plays without a hiccup.... One of the best media player in the market. The price of this media player is also reasonable and not expensive.

Another advantage is that your computer shall become free to do other things...

rraod said:

I am suggesting you an alternative method of watching movies rather than giving a solution to your problem with Windows 7 Computer.

Instead of using a computer to play movies on a HDTV, try using WDTV Live media player (a small hardware box, looks like a compact USB HDD from Western Digital with a remote control) with one or two usb HDDs (upto a max of 2TB) containing all the media (mp3s, movies, avi, mkv, mp4 etc, photos like JPGs etc...) connected to a HDTV by a HDMI cable. You will get full HD video with DTS passthrough, and an option to connect a Dolby 5.1 surround home theatre to get the best of everything.

There is a lot of difference in watching the movies on a HDTV in 1080i rather than watching movies on a computer connected to a TV.

I have been using this setup for the last two years (minus 5.1 surround home theatre) and very happy with the performance. You throw any file at WDTV and it plays without a hiccup.... One of the best media player in the market. The price of this media player is also reasonable and not expensive.

Another advantage is that your computer shall become free to do other things...

Thanks but I am looking for a cheaper solution :)