connecting two networks

I have a 192.168.1.x network connected via router to the internet. We have just added on to our IT structure and now have grown beyond the 254 limit of this address. I have configured a win2k machine as a router which leads to a 10.x.x.x network. are there any rules about hooking two private networks together. I seem to be having one DNS issue on my 10.x.x.x network. it can’t get the www location right for the company external webpage which is on the 192.168.1.x network. Any suggestions?