Open webpage from web service

all that i need now is:
1- The windows service should pop-up something saying there is a new application to be downloaded in case the webservice replied by val=1 and link for an exe file.
these file can be downloaded in the pc so the user can install it .
N.B: Like windows update link and pop-up that is shown in the taskbar that telling us that there is a new update and you can download it from this link
so that
The user should click on the pop-up and click on the link on the pop-up, to download the new application, like he downloaded the windows service before.

can anyone tell me the idea about doing this task??

write html page that should popups. place it somewhere in physical directories. Than from webservice call your html page like

Process.Start(“your webpage with path”);