Working old monitor doesn't work with old graphics card

Hi all, I got given my brother's old system and have upgraded it alittle to replace my even older system. He used the on board graphics but I took out my GeForce card and installed it and that's fine.

However, I thought I would keep the old system and found an old All In Wonder Radeon 32MB card so installed that. My problem is with his older and smaller monitor I don't get a windows desktop display. When I start it up it goes through the POST (and passes) then I can see the BIOS stuff and it then goes onto the XP loading bit but then the monitor 'switches' off so that the green light switches to orange and I get 'no signal'.

The odd thing is the monitor is working and was fine with windows 98. I have also connected my current (larger monitor) to it to test if it is the old radeon card but it works fine then. I've changed the resolution to 800 x 600 to make sure it wasn't because the monitor didn't support the higher resolutions that I am used to with my current monitor.

Both monitors are crt, my current is a 19" illayma and the other is at least 10 years old a Daewoo and is a 14/15" model. I have to use a dvi to analog converter with both monitors to connect them to either of the systems.

Any ideas?