PPC MAC G3 Will Not Install with SLA

My blue and white G3 PPC will not get passed the initial install screen. When i select sla, for the install method, the screen flashed to the rom setup then back then goes blank, and the monitor says the input is not supported.

So I am stuck here, as i cant see what is going on… when i press enter it seems to do something, so i am assuming the program is running.

I reset the rom etc, deep reset as well, all to no change, i tried a few different screen, but no luck

Any ideas would be very helpful

Video card is ATI