diff --git a/docs/sources/set-up/install/windows.md b/docs/sources/set-up/install/windows.md
index 7d7be8a6572..a6836f5df2a 100644
--- a/docs/sources/set-up/install/windows.md
+++ b/docs/sources/set-up/install/windows.md
@@ -73,6 +73,8 @@ To do a silent install of {{< param "PRODUCT_NAME" >}} on Windows, perform the f
 - `/DISABLEREPORTING=<yes|no>` Disable [data collection][]. Default: `no`
 - `/DISABLEPROFILING=<yes|no>` Disable profiling endpoint. Default: `no`
 - `/ENVIRONMENT="KEY=VALUE\0KEY2=VALUE2"` Define environment variables for Windows Service. Default: ``
+- `/FORCEREGISTRY=yes` At the start of installation, delete all Alloy registry keys and then run the rest of the install as normal so that install options such as `/STABILITY` and `/DISABLEREPORTING` are written fresh.
+  By default, the installer preserves existing registry values on upgrade; use this flag to reset them and apply the options passed on the command line, and to remove any old or unused registry keys from previous versions.
 - `/RUNTIMEPRIORITY="normal|below_normal|above_normal|high|idle|realtime"` Set the runtime priority of the {{< param "PRODUCT_NAME" >}} process. Default: `normal`
 - `/STABILITY="generally-available|public-preview|experimental"` Set the stability level of {{< param "PRODUCT_NAME" >}}. Default: `generally-available`
 - `/USERNAME="<username>"` Set the fully qualified user that Windows uses to run the service. Default: `NT AUTHORITY\LocalSystem`
diff --git a/packaging/windows/install_script.nsis b/packaging/windows/install_script.nsis
index 367f233efa8..d4789e2fff4 100644
--- a/packaging/windows/install_script.nsis
+++ b/packaging/windows/install_script.nsis
@@ -44,6 +44,7 @@ Var StabilityFlag
 Var User
 Var Password
 Var AuthFlag
+Var ForceRegistry
 
 # Pages during the installer.
 Page license
@@ -66,10 +67,19 @@ Section "install"
   ${GetOptions} $PassedInParameters "/CONFIG=" $Config
   ${GetOptions} $PassedInParameters "/USERNAME=" $User
   ${GetOptions} $PassedInParameters "/PASSWORD=" $Password
+  ${GetOptions} $PassedInParameters "/FORCEREGISTRY=" $ForceRegistry
 
   # Calls to functions like nsExec::ExecToLog below push the exit code to the
   # stack, and must be popped after calling.
 
+  # When /FORCEREGISTRY=yes, delete all Alloy registry keys at the start so the
+  # rest of the installation can proceed as normal and write fresh values. This
+  # also cleans up any old or unused keys from previous versions.
+  ${If} $ForceRegistry == "yes"
+    nsExec::ExecToLog 'Reg.exe delete "HKLM\SOFTWARE\GrafanaLabs\Alloy" /reg:64 /f'
+    Pop $0
+  ${EndIf}
+
   # Preemptively stop the existing service if it's running.
   nsExec::ExecToLog 'sc stop "Alloy"'
   Pop $0
@@ -174,7 +184,6 @@ Function CreateDataDirectory
     Return
 FunctionEnd
 
-
 # InitializeRegistry initializes the keys in the registry that the service
 # runner uses. If the registry values already exist, they are not overwritten.
 Function InitializeRegistry