How to keep registry even though uninsdeletekey was specified in Inno Setup

Annoyingly I specified the uninsdeletekey flag in my installer:

Root: "HKA"; Subkey: "Software\Company\Application"; Flags: uninsdeletekey

Similar questions:

• How to keep registry keys after uninstall with Inno Setup
• Registry Inno Setup uninsdeletekey but not on upgrade

The second question is more related to my issue. But I am not in a position to modify any uninstaller, as proposed in the answer.

It has been like this for 20 years! But I have now created two installers for the same program. One for 32/64 respectively and during installer they remove the old application.

On the upside,no user data is lost. On the down down, all data in registry is lost. I had a look at the command line switches for the uninstaller and there seems to be nothing to prevent this happening.

At the moment the only solution I can think of is:

1. Run bespoke tool to extract the key using original user account.
2. Uninstall old application.
3. Install new application.
4. Run bespoke too to import the key back in using the original user account.

Am I reinventing the wheel here? I am trying to see if there is an existing elegant solution to this problem.

If I didn’t do that all the settings would still be there.

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I stumbled on this question:

• How to export a registry in c#

In one of the answers it says about using reg.exe to export the key. So my updated idea now is:

1. Run reg.exe with original user account if possible to create the file.
2. Uninstall
3. Install
4. When app starts look for presence of this file if exists use reg.exe to import it.

Either that or write my own tool to do the same.

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I confirm that step one works:

ExecAsOriginalUser(ExpandConstant('{sys}\reg.exe'), \
    'export "HKEY_CURRENT_USER\Software\Company\Application" "d:\test.txt"', \
    '', SW_HIDE, ewWaitUntilTerminated, ExportRegResult);
    Log(SysErrorMessage(ExportRegResult));

But I hardcoded it with a d:\test.txt. I can't find out how to get a temporary file name, for us to copy into the user data folder at the end of the installation.

Imo, that's the best solution (or don't run the old uninstaller)

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To get a path to a temporary folder, to temporarily store the registry, use {tmp} constant:

ExpandConstant('{tmp}\backup.reg')

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Additionally, the ExecAsOriginalUser and HKEY_CURRENT_USER do not match with the HKA Registry entry in your old (un)installer.

Imo you should:

• Use Exec – to run the reg with the same privileges and under the same account with which your old (un)installer operates.
• Use HKEY_LOCAL_MACHINE when IsAdminInstallMode is true – to match HKA behaviour.

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For some examples of reg.exe error handling from Inno Setup, see:
Creating registry key for logged in user (not admin user) in Inno Setup