Remove previous InnoSetup install

packages/putty.xml

@@ -12,6 +12,10 @@
 
         <check type="uninstall" condition="versiongreaterorequal" path="PuTTY release %PKG_VERSION%" value="%PKG_VERSION%"/>
  
+        <install cmd='%COMSPEC% IF EXIST "%INSTALL_PATH%\unins000.exe" "%INSTALL_PATH%\unins000.exe" /silent /norestart'>
+            <exit code='0' />
+            <exit code='1' />
+        </install>
         <install cmd='msiexec /qn /norestart /i "%SOFTWARE%\putty\putty-%PKG_VERSION%-installer.msi"' />
 
         <upgrade include='install' />