problem compiling a module!

[Luis Gustavo Madrigal Salazar <tavo@scratchy.emate.ucr.ac.cr>]

I have a realtek 8139 compatible network card, and I downloaded the kernel
2.2.14 sources. And evrything compiled fine!..except that 'make xconfig'
doesn't allow me to select the realtek 8139 as a module...it appears
disabled!! How do I compile the rtl8139.o module???