diff --git a/packaging/windows/installer.nsh b/packaging/windows/installer.nsh
index ddd97de..8911994 100644
--- a/packaging/windows/installer.nsh
+++ b/packaging/windows/installer.nsh
@@ -127,6 +127,10 @@ Var FinalInstDir
   !insertmacro progressStatus "Replacing Farm Control with the new version..."
   DetailPrint "Replacing Farm Control with staged update..."
 
+  ; The install section ran SetOutPath into the install tree; a directory that
+  ; is any process's working directory cannot be renamed, so move out first.
+  SetOutPath "$TEMP"
+
   ; Clear a leftover .old from a previous interrupted update.
   ${If} ${FileExists} "$FinalInstDir.old"
     DetailPrint "Removing leftover Farm Control.old..."
@@ -137,34 +141,46 @@ Var FinalInstDir
     !insertmacro progressStatus "Waiting for Farm Control to release install files..."
     DetailPrint "Waiting to rename install directory to Farm Control.old..."
 
+    ; Retry every 500ms; success is verified on disk rather than via the
+    ; error flag, which Rename does not set reliably.
     StrCpy $R7 0
     swap_rename_old_retry:
-      ClearErrors
       Rename "$FinalInstDir" "$FinalInstDir.old"
-      ${If} ${Errors}
-        IntOp $R7 $R7 + 1
-        ${If} $R7 < 60
-          Sleep 500
-          Goto swap_rename_old_retry
-        ${EndIf}
-        !insertmacro progressFailure "Could not move the previous Farm Control installation aside."
-        Abort
+      ${IfNot} ${FileExists} "$FinalInstDir"
+        Goto swap_rename_old_done
       ${EndIf}
+      IntOp $R7 $R7 + 1
+      ${If} $R7 < 120
+        Sleep 500
+        Goto swap_rename_old_retry
+      ${EndIf}
+      !insertmacro progressFailure "Could not move the previous Farm Control installation aside."
+      Abort
+    swap_rename_old_done:
+      DetailPrint "Install directory renamed to Farm Control.old"
   ${EndIf}
 
   !insertmacro progressStatus "Activating new Farm Control installation..."
   DetailPrint "Renaming Farm Control.new to Farm Control..."
 
-  ClearErrors
-  Rename "$INSTDIR" "$FinalInstDir"
-  ${If} ${Errors}
+  StrCpy $R7 0
+  swap_rename_new_retry:
+    Rename "$INSTDIR" "$FinalInstDir"
+    ${If} ${FileExists} "$FinalInstDir"
+      Goto swap_rename_new_done
+    ${EndIf}
+    IntOp $R7 $R7 + 1
+    ${If} $R7 < 20
+      Sleep 500
+      Goto swap_rename_new_retry
+    ${EndIf}
     ; Best-effort rollback so the previous install is usable again.
     ${If} ${FileExists} "$FinalInstDir.old"
       Rename "$FinalInstDir.old" "$FinalInstDir"
     ${EndIf}
     !insertmacro progressFailure "Could not activate the new Farm Control installation."
     Abort
-  ${EndIf}
+  swap_rename_new_done:
 
   StrCpy $INSTDIR $FinalInstDir
   !insertmacro progressLog "installer:STATUS:Update files activated"