[1llusion]

I'd personally use Nmap, like Ex094 said. If you absolutely need a GUI, grab Zenmap, it does the exact same as Nmap. Good luck

When I do the nmap scan of the IP's while they're on my network I'm getting:

Note: Host seems down. If it is really up, but blocking our ping probes, try -Pn

Try adding the -Pn parameter then
Tell us what was the result, also, please include what options you used when scanning (you can just paste the whole command here), so we can see what you were exactly doing and point you to the right direction