Networking a Mac (that has Windows xp64 installed) to a PC

Hi,

I'm trying to do the above - i thought this would be simple as when i
networked my PC to the Mac when running Mac operating system, i.e. i
use the 'add network place' wizard and enter... \\ip address\username
etc but if i type this into the Mac (when using/running Windows) it
can't find that connection.

Also, when using Windows on the Mac I cant find an ip address of the
Mac - i tried typing 'ipconfig' into the command manager and no ip
addresses were shown

Do I need to set this up another way?

Thanks.