i am a problem with dt and i don't know why

it works but not with default g drive. I have to select the option to use 2 drives and then drive I works. Drive G keeps asking for a disc to be inserted into the drive (even with a iso loaded). I works perfectly fine

What gives this didn't use to happen.

I am running
win xp pro
p3 750
524 mg

2 cd roms (sony DVD and lg cd writer)
I have clone cd with their virtual drive and dt 3.26