packaging: properly unregister Alloy when uninstalling on Windows

grafana/agent#6550 fixed an issue where the service settings were not
being removed properly, but inadvertedly broke the process of removing
the application from the Add/Remove programs list.

Alloy is registered as a program to the 32-bit registry, and so it must
be removed from the 32-bit registry and not the 64-bit registry.

Fixes #165.

As a temporary workaround to this bug, users should delete
HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\Alloy from the
32-bit registry.

CHANGELOG.md

@@ -7,6 +7,14 @@ This document contains a historical list of changes between releases. Only
 changes that impact end-user behavior are listed; changes to documentation or
 internal API changes are not present.
 
+Unreleased
+----------
+
+### Bugfixes
+
+- Fix an issue on Windows where uninstalling Alloy did not remove it from the
+  Add/Remove programs list. (@rfratto)
+
 v1.0.0 (2024-04-09)
 -------------------
 

packaging/windows/install_script.nsis

@@ -239,9 +239,10 @@ Section "uninstall"
   RMDir /r "$INSTDIR"                # Install directory.
   RMDir /r "$APPDATA\${APPNAME}"     # Application data.
 
-  # Remove service and uninstaller information from the registry.
+  # Remove service and uninstaller information from the registry. Note that the
+  # service settings are stored in the 64-bit registry (so we use /reg:64),
+  # while the uninstaller information is stored in the 32-bit registry.
   nsExec::ExecToLog 'Reg.exe delete "HKLM\SOFTWARE\GrafanaLabs\Alloy"  /reg:64 /f'
   Pop $0
-  nsExec::ExecToLog 'Reg.exe delete "HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\${APPNAME}"  /reg:64 /f'
-  Pop $0
+  DeleteRegKey HKLM "Software\Microsoft\Windows\CurrentVersion\Uninstall\${APPNAME}"
 SectionEnd