Since you have hardware constraint, you have to go different approach. You can't install OS Windows 2008 R2 64 bit.
Hence, best approach is following:

1. Download and install VMware player from their site and install it.

2. Create virtual machine in that VMware player environment and install OS Windows 2008 R2. It will take it even though your it is 64 bit OS.

3. Set up Static IP and Default gateway IP in IPv4 properties from control panel.

4. Then run dcpromo.exe from command prompt or powershell environment. It will create new forest and new domain and new domain controller aka Active Directory.

Do this and let me know. By the way, are you a student or IT professional? If you are a college student these activities may be beyond your requirement for your classes. These tasks are for actual enterprise environment. If you know these things now, you will make heck lot of money later. Good Luck