these are the things that i can suggest as of now:
1. If your samsung monitor comes with an installer cd, try installing it for windows 7. Though we rarely need to bother with the monitor installer, there might be some color or monitor specific settings there that windows 7 should know.
2. Update to the latest nvidia 9500 GT drivers
3. Make sure that your power supply is at least 350W -- this is per the specified system requirements of the 9500 GT
4. The specifications page of the 9500 GT says that it has "Maximum GPU Temperature as 105 C ". Your idle temperature should definitely be less than half of 105C.
If the temperature viewer does not come with the driver, i think this link will include it http://www.nvidia.com/object/ntune_5.05.54.00.html
And yes you are using both the video card and monitor to the supported settings
Nvide 9500 GT:
Maximum Digital Resolution 2560x1600
Maximum VGA Resolution 2048x1536
1600 x 900 Display Resolution
You might want to try and see if the lines appear while playing different games/ playing full screen movies/ or just in windows programs