Search for mac addresses over my network (show all even if the host pc is closed)

"If they are off? No, they have no way to respond.

Although you don't need a tool if they are on, ping the broadcast address for your network then grab them with arp:

C:\>ping 10.100.1.255

Pinging 10.100.1.255 with 32 bytes of data:

Reply from 10.100.1.235: bytes=32 time<1ms TTL=64
Reply from 10.100.1.235: bytes=32 time<1ms TTL=64
Reply from 10.100.1.235: bytes=32 time<1ms TTL=64
Reply from 10.100.1.235: bytes=32 time<1ms TTL=64

Ping statistics for 10.100.1.255:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 0ms, Average = 0ms

C:\>arp -a

Interface: 10.100.1.174 --- 0x4
Internet Address Physical Address Type
10.100.1.175 00-03-ff-a2-c0-95 dynamic
10.100.1.178 00-03-ff-46-df-1d dynamic
10.100.1.196 00-03-ff-49-0c-30 dynamic
10.100.1.220 00-03-ff-46-99-37 dynamic
10.100.1.227 00-03-ff-46-95-05 dynamic
10.100.1.235 00-03-ff-46-de-1e dynamic
10.100.1.239 00-03-ff-46-9f-c1 dynamic"