It sounds like your hard drive has failed.
The error message you are getting is because your system is trying to boot from the network card and either cannot find a network resource or a boot ROM.
Do you hear a tick or clunk sound from the computer when you boot up? That is a sure sign that the hard drive has failed.
Start by entering BIOS setup and see if the BIOS detects your hard drive. If the BIOS sees the drive, you may have just lost the boot files.
If the BIOS does not detect your hard drive, you will need to open the case and make sure that the power and data cables are plugged into the hard drive and seated.
If the cables are seated and you still get no response from the drive, the drive is most likely dead.
You will need a new drive and a set of recovery disks from Compaq to get back going again.
Chas