dual displays -can't change resolution individually

Question: How can I set the resolution of each display individually? Details below:

I have the new iMac 21" and an LG W2252 display from my old PC. I'm a newly converted mac user. I connected it to the imac and it worked. But the resolution is horrible. I can change the resolution when the displays are mirrored. But then when I uncheck mirror the resolution for each display cannot be changed individually. The LG goes out of range and won't show anything until I bring the resolution down and mirror the imac. Is this problem with the LG or the mac? Or both not being compatible with each other?

I have a dell LCD that's not that great a monitor, but when I connect that one the display can be set to it's own resolution.

Any help would be appreciated.

greenboy said:

Does the iMac identify the LG monitor as an LG? Like, when you look at the monitor profile in the display preferences, what does it say? Have you tried clicking on the detect display button?

Click to expand...

Actually, no. It just says VGA display. I'll try the detect display button and report back.

I tried using the detect display, but it still doesn't recognize the LG monitor. It does recognize a dell though.

Could it have anything to do with using VGA over DVI connection? The LG has both types of connections. I bought the mini display port to VGA adapter from apple. I will exchange it if it will make a difference.