There are reverse arp lookup utilities for Unix, but for Windows use Tek-Tip member ricpinto's trick:
Let say your network is class c with the address range 192.168.0.1 - 192.168.0.254 then run the command below:
c:\>FOR /L %i IN (1,1,254) DO nbtstat -a 192.168.0.%i>>nbtstat.txt
(1,1,254) - (start,step,end)
%i - variable.
nbtstat.txt - Resulting file.
This event will take awhile . .
Now open file nbtstat.txt and search for the MAC address you're looking for.