Skip to main content

Fixing Deployment.AddInAlreadyInstalledException.



If you are building any VSTO for any of the office applications, then its quite common to run into this issue.


The error message would say that

"The customization cannot be installed because another version is currently installed and cannot be upgraded from this location. To install this version of the customization, first use Add or Remove Programs to uninstall this program: TestUpdatedVersion. Then install the new customization from the following location: file:///D:/Samples/TestUpdatedVersion/bin/Debug/TestUpdatedVersion.vsto ********** Exception Text ********** Microsoft.VisualStudio.Tools.Applications.Deployment.AddInAlreadyInstalledException: The customization cannot be installed because another version is currently installed and cannot be upgraded from this location. To install this version of the customization, first use Add or Remove Programs to uninstall this program: TestUpdatedVersion. Then install the new customization from the following location: file:///D:/Samples/TestUpdatedVersion/bin/Debug/TestUpdatedVersion.vsto at Microsoft.VisualStudio.Tools.Applications.Deployment.ClickOnceAddInDeploymentManager.VerifySolutionCodebaseIsUnchanged(Uri uri, String subscriptionId, Boolean previouslyInstalled) at Microsoft.VisualStudio.Tools.Applications.Deployment.ClickOnceAddInDeploymentManager.InstallAddIn()"


So let me explain a fool proof way to troubleshoot this. Would be quite useful for Support Engineers.


  1. Go to Control Panel and search for this application plugin. If its listed then try to uninstall this and then re run the set-up. If its not listed or re-running the setup.exe fails then continue with step 2.
  2. Try cleaning up registry and installed file list by using a "Fix it" package from Microsoft, available here https://support.microsoft.com/en-us/mats/program_install_and_uninstall
  3. Now most probably the application is uninstalled but it has left behind some registry. So let clear them. 
  4. Press Start+R. In run command prompt type regedit and press enter.
  5. Clear any application related keys from 
  6. In registry editor go HKEY_CURRENT_USER\Software\Microsoft\Office\/Addins/
  7. to HKEY_CURRENT_USER\Software\Microsoft\VSTO\SolutionMetadata\{GUID} and clean up the entry for the VSTO. Check on the right side of the screen to figure out the right registry entry.
  8. Then check if there is an entry for HKEY_CURRENT_USER\Software\Microsoft\VSTA\Solutions\{GUID}. If there exists an entry then clear this up too. 
  9. Now First you would have to install Visual Studio 2013 Community edition from here https://www.visualstudio.com/en-us/products/visual-studio-community-vs.aspx,
  10. This should result in download of mage.exe with its dependencies. https://msdn.microsoft.com/en-us/library/acz3y3te(v=vs.110).aspx Then going to C:\Program Files (x86)\Microsoft SDKs\Windows\v7.0A\Bin you should see mage.exe there.
  11. Then cd into the location for mage.exe in commandprompt.
  12. Run the following command there: mage.exe -cc. It should produce an output "Application Cache Cleared"
  13. Now reinstall the VSTO by running the setup.exe. This time it should go through for sure. If it does not then please do leave a comment.

Popular posts from this blog

Why India Hasn’t Built Its GPT Moment (Yet)

India has the world’s third-largest startup ecosystem, a thriving developer base, and a mobile-first population larger than the US and Europe combined. Yet, no GPT-4. No DeepMind. No Amazon-style platform. Why? Innovation Isn’t Accidental—It’s Engineered The Zerodha Daily Brief recently asked why India hasn’t built a global product company like Apple. The key argument: India isn’t building for the world. It’s solving for local constraints, scale, and affordability—but global scale requires deep IP, design, and tech differentiation. It’s not just about software, it’s about systems thinking. More importantly, it answers the question: Why do countries innovate? The answer isn’t just genius or ambition—it’s incentives and ecosystems. The U.S. Defense Department, for example, accounted for nearly 70% of federal R&D funding during the Cold War. China has pumped billions into semiconductors and AI with long-term national alignment. These aren’t short-term bets—they are strategic, delibe...

The Death of the Stubborn PM

Product Management is undergoing a seismic shift, much like programming did when compilers replaced assembly language or when Agile dismantled waterfall dogma. Stubborn PMs who cling to outdated rituals—like treating PRDs as sacred texts—will fade into irrelevance. The future belongs to those who embrace AI as a collaborator, not a threat.   AI Will Disrupt the Tactics, Not the Thinking   Historically, tools abstracted manual work: compilers automated code translation, A/B testing replaced gut-driven debates. Similarly, AI will automate tactical PM tasks—data aggregation, routine prioritization, even drafting specs. But this is liberating, not limiting.   The stubborn PM obsesses over *how* to write a PRD; the adaptive PM focuses on *why* a product should exist. AI can’t replicate judgment calls that demand intuition: interpreting unmet customer needs, balancing ethics with growth, or navigating ambiguity when data is sparse. As AI handles execution, the PM...

From Stubborn to Smart: How I Learned to Use AI as a PM

Listen to the article in podcast format on PM-AI Diaries channel on Spotify! Ever since I published "The Death of the Stubborn PM" back in February, my inbox has been buzzing with one big question: “Okay, I get that AI is the future for product managers—but how do I actually use it?” It’s a fair ask. In that piece, I argued that PMs who resist AI are doomed to fade away, like dinosaurs refusing to evolve. As I wrote, “The stubborn PM who clings to old ways will die out, replaced by those who harness AI’s power while leaning into what makes us human.” Now, people want the playbook. So, let’s walk through it with a story—my own journey of figuring this out, backed by some sharp insights from MIT Sloan’s "When Humans and AI Work Best Together—and When Each Is Better Alone" . The Wake-Up Call Picture me a few months back: a PM buried in work, juggling a dozen tasks, and feeling like there weren’t enough hours in the day. Writing user stories, sketching ideas, track...