diff --git a/src/ProductInfo.inc b/src/ProductInfo.inc
index fc3e2ab1ab..0bc8d97ce1 100644
--- a/src/ProductInfo.inc
+++ b/src/ProductInfo.inc
@@ -1,12 +1,14 @@
 ; Included by the NSIS installer script
 ; Don't forget to also change ProductInfo.h!
 
+; a friendly string to refer to the product
 !define PRODUCT_FAMILY "StepMania"
 
-; see ProductInfo.h for use descriptions
-!define PRODUCT_ID "StepMania"
+; PRODUCT_ID must NOT be "StepMania" unless you want people to uninstall 3.9
+; when they install StepMania 5.
+!define PRODUCT_ID "StepMania 5"
 !define PRODUCT_VER "v5.0 alpha 1"
-!define PRODUCT_DISPLAY "${PRODUCT_ID} ${PRODUCT_VER}"
+!define PRODUCT_DISPLAY "${PRODUCT_FAMILY} ${PRODUCT_VER}"
 !define PRODUCT_BITMAP "sm5"
 
 !define PRODUCT_URL "http://www.stepmania.com/"