As you might guess, duplicate IP addresses are not acceptable in a network.
You can find your PC's IP address by opening a command prompt and typing
IPCONFIG, then hitting return. If you have a small network, do this on all
PCs, and if you find a duplicate, change one of them.
An IP address should look something like: abc.def.ghi.xyz
In general the first three sets of numbers are the same within a network.
The last three (xyz) must be unique.
Note that network preipherals, like printers, xerox machines, scanners, etc
also have IP addresses, although I am not sure how to list them, not having
a network at home and having proffessional IT support at work. But, I
suspect there is some simple command to list all devices. You might want to
try the built-in help for IPCONFIG, that is, use (space)/? after the command
to list options.