MAC G5 interface with dell screen - please help!!!!

Okay, a couple of weeks ago the screen for my mac G5 crapped out (23 inch HD Cinema display) - Bad news.
Good news - I also have a pc screen handy that I am trying to use on my G5.
Dillema: I bought a DVI-VGA cable and am trying to interface the G5 with my Dell screen (Optiplex GX260). Problem is, I get the apple start up Icon (grey screen with the gadget turning) then after that my screen goes black.
When I hit buttons on the screen it says the screen is in power save mode, blah blah blah, hit this key - nothing happens.
I have gotten it to the point where it says auto adjust is in progress, then it goes to the black screen.
Is there anyway I can fix this? I know the cable works, because I get the start up screen - it's just when I get to what would be the desktop, it craps out.
I am guessing that I need to change the resolution or something. I have tried the whole resetting PRAM deal, but got nothing. Please help! Any information will be greatly appreciated. Thanks!

Adjusting MacBook replacement screen brightness.

you can try F7 to try and toggle to the new screen but it probably won't work.

the only other thing to do is change your PRAM battery, which is the silver round watch battery inside under a clip. It's a lithium 3v you can buy anywhere for a couple of pounds/dollars. if you have had your mac on for a long time, i.e. don't turn it off at nights it may have run out.

otherwise it's something more serious like a kernel panic or the logic board. see other forum threads to find out about these.