I have a customer who has several PCs in a plant that are not connected to the internet. My team has developed a vb.net application via Visual Studios 2008 that needs to be deployed to each of these plant PCs. The code has been in developement for a couple of years now and we have been using ClickOnce to deploy updates to the software. We publish in VS2008, put the publish file on a thumb drive or CD and walk out to each PC, uninstall the old version, install the new version and make several changes in the settings that are specific to each PC. We use ClickOnce as apposed to Windows Installer because it is simpler and we get a nice backlog of old versions when using ClickOnce, in case we have to roll back. The problem is this. Say one developer creates an update today(version 2.0.0.275) and installs it on a PC. He creates a new update tomorrow(version 2.0.0.276) and installs it again, he can simply run the setup.exe and the new version overwrites the old version, the settings are carried through from the old version to the new, and everything is great, the people rejoice
BUT, if a second developer creates an update the next day(version 2.0.0.277) on a different PC and goes to install it, if he does not first uninstall the old version, he will create a duplicate program with a " - 1" beside it, and the settings will not carry through and the people do not rejoice 
I have been researching this problem for days now to figure out what we need to do to make this installation as simple as possible so that when we are off site, the customer can install the update themselves without having to call us with a million questions (petty, yes I know, but the customer is always right...). I have looked into using some sort of certificate that is passed around with the source code so the install always recognizes that the new version is an update but I get can't find any help and I'm not sure if that even makes since. Can someone please help me understand what is going on here, and how I can resolve this problem?
Thanks a ton!
BUT, if a second developer creates an update the next day(version 2.0.0.277) on a different PC and goes to install it, if he does not first uninstall the old version, he will create a duplicate program with a " - 1" beside it, and the settings will not carry through and the people do not rejoice I have been researching this problem for days now to figure out what we need to do to make this installation as simple as possible so that when we are off site, the customer can install the update themselves without having to call us with a million questions (petty, yes I know, but the customer is always right...). I have looked into using some sort of certificate that is passed around with the source code so the install always recognizes that the new version is an update but I get can't find any help and I'm not sure if that even makes since. Can someone please help me understand what is going on here, and how I can resolve this problem?Thanks a ton!