Make sure you have the latest Adobe Flash, Shockwave, and Sun's Java installed. Also make sure you have installed all the Windows Updates and service packs for your computer's operating system
try checking your cables it sounds to me like you have a bad cable from your vga from your computer to your monitor . try wiggling your cord?.best of luck
also try unpluging your vidio card 4 or 5 times to clean the contacts and then reconnect the monitor to see if that helps. best of luck
"only that happens when i watch videos..... maybe its the codec which i read somewhere"
What kind of videos? YouTube or others?
1. How "large" is the green stuff? Is it covering like 5% or 25% of the screen?
2. What kind of video format are you trying to watch? i.e. is the file's name like "prisonbreaks1e4.wmv" or .avi and so on...
Because if it is in .mp4 (mp-format), the green stuff might very well be a failed update of that specific area in the movie-file. This is partly how the .mp#-codec works.
We'll have to get back on that if the format is a mp#-format.
3. Does this happen to all movie-files?
If it does, then it's probably not the codecpack.
Finally, provided you have more than 1 media player (if not; ignore question #4).
4. What Media Player does/does not show this problem?
This can also happen in YouTube-videos by the way.