In addition to the BIOS setting, you also need to also enable power on by network on the server in SW. I don't know about 98/me but in XP you take the following steps:
1) Goto control panel
2) Select System Icon
3) Select Hardware / Device Manager
4) Select your NIC
5) Select properties
6) Select power managment tab
7) make sure that "allow device to bring system out of standby" is checked
Computers seem to be a little quirky on how they will allow you to wake them. My HTPC will wake from any state (off/sleep/hibernate). My Server will only wake if I put it into hibernate. If it looses power while hibernated or if I shutdown I have to manually restart with the power button. So at first if it doesn't wake, try to put it into a different sleep state.
The next step is to send the "magic packet" this requires you to intall an applet on your systems that will be waking up the server (as well as getting the MAC address you are trying to wake). You can get the MAC address by going to your server, getting to the DOS prompt, and typing ipconfig/all...the physical address is what you are looking for. I use a DOS command based applet to send the magic packet.
Good luck!