Domain Integration

I need a solution to integrate two(2) DC’s to one single network.
Both DC’s are Windows 2003 and the only connection now is via Juniper VPN
Routers.ISP Prvider is the same for both offices, but VPN access spee via Router is not fast
I been ask me to integrate both DC’s to single network and make both
DC available to users located in office 1 and office 2
IP addr of DC 1 is 100.100.xxx.xxx s.m 255.255.0.0, d.g 100.100.xxx.10
IP addr of DC 2 is 10.10.xxx.xxx s.m 255..0.0, d.g 10.10.xxx.0
The main reason to do this is both companies been integrated to single owner
ship and users been changed locations
They are other servers involved SQL, TS Server(Citrix)
Please help me with this issue…
Thanks