Problems with SBS 2003 and LCS 2003

Hi experts
On our SBS 2003 server, I had installed LCS 2003. We had some Vista workstations but Messenger 5.1 would not run with Vista. We canned LCS in support of Office Communications server. To utilize as a secondary domain controller, we bought one more server and then on that machine we installed OCS.
After months of problem by Vista and OCS we went back to LCS 2003 again but we were unable to use it again, yet when we installed it on the secondary DC.
Then we uninstalled LCS 2003 from SBS 2003 and ran OCS 2007 on second domain controller. It worked but with many troubles. Then we uninstalled OCS 2007 from second domain controller and again installed LCS 2003 that was originally installed on SBS onto the second DC. The installation was good, but for some reason the clients were not able to log in.
LCS and OCS left all of the SIP names in active directory after ending all of the install/uninstall and I was unable to remove them. Please give me a suggestion. Thanks in advance.
