Try to reduce the resolution of your computer down to 640x480. Your TV might not be able to handle higher resolutions.
You can also download a software
powerstrip where you can adjust your TV settings just like a computer monitor. This is usually used in HTPC applications but I have tried this hooking a computer to my 36 widescreen TV with great results.
I also suggest that you use at least the S-video input of your TV for a better and clearer video output.
Hope this helps.
