no graphics M7VIG mobo

I replaced a toasted mobo with an M7VIG 400. I don't have windows install media, only a "restore" cd which I doubt will work now since the original mobo was a Compaq, and it ain't a compaq no mo'.

I have video during the POST, and I can go into the BIOS setup via the on-board Unichrome graphics port. After Windows ME puts up its logo, however the screen goes black. The drive is running, so I'm sure Windows continues to load. On a whim I put an Nvidia GeForce 400 in the AGP slot and it works fine - in fact I'm using it now

I've tried loading all the drivers on the CD that came with the mobo as well as from the VIA website. Frustratingly, the WINS3ID program says I have no S3 graphics hardware in the system.

Does installing a card in the AGP slot disable the on-board graphics?

Is there something I can do to force Windows to recognize the S3 Unichrome chipset on boot? Maybe even run in default VGA mode so I can load the S3 drivers?

If the Nvidia card works, do I really care about the Unichrome grpahics anyway? (In other words am I sacrificing something by using the Nvidia card instead of the on-board graphics?) This is not my machine, so I'm not looking to spring for a high-end graphics card for it.

Thanks in advance, and Happy New Year to all!!!

Jay