Gateway has no video output..

I hope this is the right Forum: This is about a unit that I inherited.
I have this Gateway ATXAEG LX2 700s without a HD. It had been running XP, but I have
installed a HD with 98SE. It worked fine except neither the DVD or CD,, though they show on the BIOS, worked. I also installed a RAGE128 PRO 32MP AGP video board,
and every thing worked fine. This morning I switched on, and there is no video. Checked
board installation, changed back to original board, tried two monitors....nothing. The indicator light on the Monitor which usually changes from Amber to Green when it sees
signal, remains Amber. And as mentioned have not yet sorted out the CD. They accept disks and run, but no output.
Any suggestions will be appreciated....
Thanks..

 

Might want to start with the power supply...

 

Thanks ekim68, but I found that after checking that all boards and plugs were securely
plugged in, the system started ok. Now I only have to get the CDRom the DVD
working, but I'll create a new post for that....
Thanks again.