Long sotry short"
Compaq presario CQ60 here.
White screen with colored lines vertical or horizontal ( can't remember which). External video on an external monitor will not work.
Tried a new inverter, same problem and no external video. Tried another compatible screen (But I'm not 100% sure if it works honestly) and got a blank black screen but I'm pretty sure the backlight is working fine in it. Tried that screen with new inverter also. No video on external monitor either.
My conclusion: Bad integrated video on the motherboard therefore no display? Or is it possible the video cable could be bad?
All of what you're saying points to bad integrated graphics but it may also be a bad video cable. In any case, try replacing the video cable first, if it doesn't do anything to make it better then the integrated graphics on the motherboard may be shot.
Check THIS out, krikle.
I know about the FN key toggles and all that. I'm pretty sure its the integrated graphics. Even if it were an LCD cable issue, it should still show up on an external monitor or no? Cause it doesn't.