can you at least get it to recognize the Empeg via the serial port?
No, 'cos I haven't got a serial cable adaptor...

First: You need to know your Mac's IP address
Where can I find this?

and whether it's a fixed address or if it gets the address from a DHCP server
How can I find out?

Second, you need to be sure the TCP/IP software is even installed on the VirtualPC at all (it might not be). Go into control panel/network, there should be a TCP/IP protocol installed.
Yep, it's there.

Third, do you have any other hard-wired ethernet devices on the network that you can ping to make sure everything else (besides the empeg) is working on TCP/IP
Firstly, I don't know anything about pinging! (Didn't realise you had to have a computer science degree to own a car stereo!!) Secondly, there's no network as such - I 'm just sat at home with my laptop.

Fourth, are you getting a proper link light at both ends of the ethernet cable that you're using to connect the empeg to
Where's the light supposed to be? I'm using a crossover cable, and I've also tried a reguar ethernet cable.

... wait... what are you connecting the empeg to?
To the ethernet port of my Mac.

Hope this doesn't sound too hopeless! : (

Sally