What model of Realtek is this? Have you checked to see if it sees it? You can do the following to see:
$ dmesg | grep Real
$ cat /proc/pci
See if anything mentions the card, and post the model as well (usually RL<model number>).
Also, remember just because it worked in Windows, does not mean it will work in Linux at all. They are completely different, and when a manufacturer will NOT release the documentation to allow the Linux Community to create the drivers; usually they won't exist.