Instead of manually pinging all IP addresses on your LAN you can use this nice command:
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Open Command Prompt and type:
FOR /L %i IN (1,1,254) DO ping -n 1 192.168.0.%i | FIND /i "Reply">> c:\ipaddresses.txt
The "-n 1" is for only 1 ping packet to be sent to each computer.
Change 192.168.0 to match you own Network ID.
This will ping all IP addresses on the 192.168.0.0 network segment and create a text file called IPADDRESSES.TXT in C:\, where it will list only the IP addresses that gave a reply.
FOR /L %i IN (1,1,254) DO ping -a -n 1 192.168.0.%i | FIND /i "Reply">> c:\ipaddresses.txt
You can, of course, modify this script and make it suit your own desire.