Running out of ip addresses.

Hello

We are running out of ip addresses in our subnet 10.164.231.xx 255.255.255.0.

What is the best solution to get more ip’s since our network is growing very fast? We have other sites with the following subnets but they are still long way to go until depletion. they use 10.164.232.xx 255.255.255.0 and 10.164.234.xx 255.255.255.0. How can I subnet our network without affecting the other sites or should we add another subnet to our network?

We use Windows Server 2003 with Active Directory.

Please, all help will be appreciated.

Thanks,