I have a 10 year old socket 7 motherboard with an AMD up running at
300Mhz with Windows 98 which was able to install a Linksys wireless
card a year back. However, when I tried to install a Realtek 10/100M
Fast Ethernet card, the operating system didn't detect it. I installed
the drivers and yet still it doesn't see the card under control panel/
system/networking.

It detects fine on an AMD Athlon motherboard running Windows 98 so
what's wrong with my old motherboard?

Thanks for your input.