Well another confusing thread.
The 9800 has min. system requirements:
-Intel® Pentium® 4, AMD® Athlon® or higher with AGP 8X (0.8v), 4X (1.5V) or Universal AGP 3.0 bus configuration (8X/4X)
http://mirror.ati.com/products/radeon9800/...0pro/specs.html
Maybe a new mobo will do it. The real reason you would need a new mobo is because you need a new CPU.
I think you meet the requirements are for a 9700.
http://mirror.ati.com/products/radeon9700/...0pro/specs.html
Maybe you can return the 9800 for 9700?
These are my thoughts.
*edit*
You say it runs fine now-I have to wonder about how your CPU handles the stress of that card?
Oh well I wouldn't do it.