_vti_bin/owssvr.dll?CS=109 Page cannot be found

_vti_bin/owssvr.dll?CS=109 Page cannot be found Recently I faced a strange problem related to Un-installation of Windows Sharepoint Services 3.0. We were upgrading an Windows Sharepoint Services 2.0 application to WSS 3.0 using In-Place upgrade wizard. We finished upgrade successfully but after upgrading we decided to go back to WSS 2.0 and start upgrade again (for some issues). We followed following approach for rollback (with an assumption that we have code and DB backup of WSS 2.0 application) 1. Un-install WSS 3.0. 2. Remove .Net framework 3.0. 3. Execute Setup of WSS 2.0 (with SP2) and go for “Reinstall or repair” option. 4. Drop all migrated databases. 5. Start deployment of WSS 2.0 application (As if you are installing it for the first time). Restore the content database and follow procedure for “Detach and Attach” content database 6. The application would be running with WSS 2.0. This plan was supposed to work perfectly as it was tested couple of times before. However while we performed it in one of our environment, we started facing issues. The one issue that took most of our nights was “Page cannot be found error” while we try to save any values in Contacts, Events, Discussion lists. At that time the browser showed url as http:///_vti_bin/owssvr.dll?CS=109 We tried so many things but were unable to understand why its happening. Then we started old configuration and recent configuration one by one. And guess what, yes… we could finally figure out the difference. While we use WSS 2.0 application, in IIS you will notice “Web Service Extensions” section next to “Application Pool” and “Web sites” section. Under the Web Service Extension there has to one entry for “Windows Sharepoint Services” with status as “Allowed”. If you don’t have such entry then try creating a new one. Make sure that you allow following DLLs a. _vti_bin\admin.dll b. _vti_aut\author.dll c. owssvr.dll d. shtml.dll Thankfully this took us to a working application and we could have a great relaxed weekend … !! Enjoy Life Subhash Dike [Please note: This solution/comment is based on personal experience and may not be authentica. This solution does not guarantee that it would react the same way anywhere else. You can refer to product documentation and authorized websites for more information.]