I think one of your hard drives has gone kaput. It may be possible that your pc is trying to boot from a HD with no OS. With the number of drives you are using, that could be your problem. disconnect the drive you boot from, load your o/s onto the drive you want to boot (or boot from another drive with an OS) and see what happens. Also, it just might be the master cable from your drive to the MB. Try swapping cables fromthe the slave IDE connector to the master IDE connector.
Sounds like your computer is trying to boot from LAN. That means it was unable to boot from the hard drive, CD-Drive, Floppy and now LAN. Assuming the boot order is set properly. You can check the boot order in your BIOS to ensure that the hard drive is the 1st device to boot from.