I have a 27" iMac Core 2 Duo 3.06Ghz (Late 2009) model. It has a ATI Radeon HD 4670. I am a web designer and bought an external monitor - ViewSonic VX2453mh-LED 24" to use with my iMac. It says that its both Windows and Mac compatible. Then I also bought a Apple Mini DisplayPort to VGA Display Adapter. Once the monitor arrives, I hook it up. It detects the monitor as VX2453, however when I set the highest resolution, the ViewSonic only shows like 3/4 of the full screen. (look at the attached picture). I also have a 13" MacBook Pro 2.7Ghz Core i7 (latest model), and it has a Thunderbolt Port. I connect the Mini DP VGA Display Adapter there, and like magic the ViewSonic monitor works with the MacBook Pro for some reason. The MBP detects the monitor as a Color LCD, and the resolution 1980x1080 works perfect (everything is crisp and clear). I then find this software called SwitchResX, and it basically helps my iMac and fixes the 3/4 display width program, and the screen now displays fullscreen, HOWEVER it's still NOT the same quality as the MBP. It's NOT crisp and clear. Text is dark and blurry and it's stretched in. And I tested the monitor with a Windows 7 PC, and it displayed much better - just like the MBP. Can someone please tell me what's the problem? Is it my iMac that has a poor graphics card and isn't able to handle an external monitor? Because the Windows 7 machine - everything looks much nicer on there, and not blurry, and same with the MBP. Maybe the MBP has a Thunderbolt port, and that helps it. OR, if the monitor I have too weak, or what? Please help. If so, can anyone recommend a 24" monitor for the iMac that will work perfectly with the Late 2009 model? I want no blurry text, 100% compatible etc.. OR maybe its the bad adapter (Apple Mini DisplayPort to VGA Display Adapter)? But I doubt it, because it works great with the Windows 7 machine, and the MBP. Any help would be greatly appreciated. THANKS in advance!