iMac and second display problem

Hi, today I connected second display to my iMac.
Problem is that it doesnt work.
I connected it like that
iMac>mini dvi to dvi>dvi to vga adaptor>vga cable>display
display is all the time on stand by
when i go to system prefs. dispaly, mac see it but it doesn't work anyway
help me guys
maybe it is dvi to vga adapter? what do you think? maybe i should take off dvi to vga adapter and vga cable and just get a single dvi to vga cable? is that might help?

i'v tried cabel and still nothing, but what i found is that i had to remove 4 pins from dvi cable to fit into mini dvi to dvi. and flat metal thing does'n fit as well. but when i hardly press them together it moves backward.
what tha f---- is that mean?

Please see first post in the following thread to fill in the blanks in your question.

http://www.mac-forums.com/forums/other-hardware-peripherals/193239-connecting-your-mac-your-tv.html

i have a iMac 2.4ghz intel core 2 duo, leopard 10.6.2,
i bought that mac a year ago, new. so it is aluminum body one iMac
i connected it by mini dvi to dvi original apple adapter.
my display is LG Flatron L1718S
name of display shows also on mac when i go to sys pref.>display
display have vga input

i connected now another display and there is same story

The mini-DVI to DVI adapter puts out a digital signal only. It does not pass thru the analog signal. This is why you're not able to connect a DVI to VGA cable to the adapter. That's also why you're having to remove the 4 pins from the DVI cable. Those pins are part of what carries the analog signal.

You will need a mini-DVI to VGA adapter and your VGA cable.
You can grab that adapter from Apple, monoprice, Amazon or any number of other places.