Thanks for your suggestion. If i change the version no. of the setup project everytime when i rebuild then it's working fine i.e.,it is not giving any msg and it's reinstalling the whole application. Upto here fine.but is there anyway to automate the process of changing the version number of setup project everytime when i rebuild.

I have installed my application which is built in C#.NET in the client machine. I have used Set-Up Project for this. After then i have done slight modifications to my application and again i tried to reinstall the application. But it is giving the message like 'Another version of this project is already installed.Installation of this version cannot continue.To configure or remove the existing version of this product, Use Add/Remove Programs on the Control Panel'. Is there any way other than uninstalling and again installing the application. Mahesh Dara.