diff --git a/ftbinstall/installer.go b/ftbinstall/installer.go
index 090f3e8..3c9db78 100644
--- a/ftbinstall/installer.go
+++ b/ftbinstall/installer.go
@@ -42,9 +42,9 @@ func InstallPackVersion(installTarget mcinstall.InstallTarget, dest string, pack
 		return err
 	}
 
-	var install *InstallSettings
-	if readJson(filepath.Join(destination, DataDir, SettingsFile), &install) != nil {
-		install = &InstallSettings{
+	var settings *InstallSettings
+	if readJson(filepath.Join(destination, DataDir, SettingsFile), &settings) != nil {
+		settings = &InstallSettings{
 			ID:      uuid.New().String(),
 			Pack:    pack.Slug,
 			Version: version.Slug,
@@ -52,12 +52,17 @@ func InstallPackVersion(installTarget mcinstall.InstallTarget, dest string, pack
 			Files:   map[string]string{},
 		}
 	} else {
-		fmt.Println("Existing installation of " + install.Pack + " v" + install.Version + " detected")
+		fmt.Println("Existing installation of " + settings.Pack + " v" + settings.Version + " detected")
 
-		if pack.Slug != install.Pack {
+		if pack.Slug != settings.Pack {
 			return OtherPackAlreadyInstalled
 		}
 	}
+	install := &Install{
+		Version:       version.Slug,
+		OriginalFiles: settings.Files,
+		NewFiles:      map[string]string{},
+	}
 
 	err = InstallTargets(installTarget, destination, version.Targets)
 	if err != nil {
@@ -112,7 +117,7 @@ func InstallPackVersion(installTarget mcinstall.InstallTarget, dest string, pack
 						forgeVersion = mcVersion.String() + "-forge" + mcVersion.String() + "-" + target.Version
 					}
 
-					if err := mcinstall.InstallProfile(install.ID, &mcinstall.Profile{
+					if err := mcinstall.InstallProfile(settings.ID, &mcinstall.Profile{
 						Name:    pack.Name + " " + version.Name,
 						Type:    "custom",
 						GameDir: destination,
@@ -130,7 +135,15 @@ func InstallPackVersion(installTarget mcinstall.InstallTarget, dest string, pack
 	}
 
 	// Write install settings
-	return writeJson(filepath.Join(destination, DataDir, SettingsFile), &install)
+	settings.Version = install.Version
+	settings.Files = install.NewFiles
+	return writeJson(filepath.Join(destination, DataDir, SettingsFile), &settings)
+}
+
+type Install struct {
+	Version string
+	OriginalFiles map[string]string
+	NewFiles map[string]string
 }
 
 // ftbinstall.json
diff --git a/ftbinstall/installer_files.go b/ftbinstall/installer_files.go
index 220250d..d19d4b1 100644
--- a/ftbinstall/installer_files.go
+++ b/ftbinstall/installer_files.go
@@ -19,7 +19,7 @@ import (
 
 // Installs the given files, for the target environment, to the given
 // destination.
-func InstallFiles(install *InstallSettings, target mcinstall.InstallTarget, dest string, files []*ftbmeta.File) error {
+func InstallFiles(install *Install, target mcinstall.InstallTarget, dest string, files []*ftbmeta.File) error {
 	// Collect the target-specific files, so we can keep an accurate count
 	// of how many files we've installed.
 	var targetFiles []*ftbmeta.File
@@ -33,24 +33,23 @@ func InstallFiles(install *InstallSettings, target mcinstall.InstallTarget, dest
 
 	// Install files for the target
 	for i, file := range targetFiles {
-		msg, err := installFile(dest, file)
+		msg, err := installFile(install, dest, file)
 		if err != nil {
-			fmt.Printf("[%d / %d] Failed to install '%s%s', ignoring file...`n", i + 1, len(targetFiles), file.Path, file.Name)
+			fmt.Printf("[%d / %d] Failed to install '%s%s', ignoring file...\n", i + 1, len(targetFiles), file.Path, file.Name)
 			fmt.Println(err)
 			continue
-		} else if msg != "" {
-			fmt.Printf("[%d / %d] %s\n", i + 1, len(targetFiles), msg)
 		}
+		fmt.Printf("[%d / %d] %s\n", i + 1, len(targetFiles), msg)
 
 		// Log the files information in the install settings
-		install.Files[file.Path + file.Name] = file.Sha1
+		install.NewFiles[file.Path + file.Name] = file.Sha1
 	}
 
 	return nil
 }
 
 // Installs the given file, to the destination
-func installFile(dest string, file *ftbmeta.File) (string, error) {
+func installFile(install *Install, dest string, file *ftbmeta.File) (string, error) {
 	dirPath := filepath.Join(dest, filepath.FromSlash(file.Path))
 	fileDest := filepath.Join(dirPath, file.Name)
 
@@ -67,10 +66,25 @@ func installFile(dest string, file *ftbmeta.File) (string, error) {
 			return "", err
 		}
 
+		hash := hex.EncodeToString(hasher.Sum(nil))
+
 		// If already exists, continue to next file
-		if hex.EncodeToString(hasher.Sum(nil)) == file.Sha1 {
+		if hash == file.Sha1 {
 			return fmt.Sprintf("%s%s found, skipping...", file.Path, file.Name), nil
 		}
+
+		// If the file previously existed, don't override if the player made changes
+		originalHash := install.OriginalFiles[file.Path + file.Name]
+		if originalHash != "" && hash != originalHash {
+			fmt.Println("************************************************************************************************")
+			fmt.Printf("%s%s has a sha1 has of '%s', when\n", file.Path, file.Name, hash)
+			fmt.Printf("'%s' was expected.\n", originalHash)
+			fmt.Printf("To prevent overriding configurations, it will be installed under %s/%s.\n", DataDir, install.Version)
+			fmt.Println("Please investigate any collisions before playing!")
+			fmt.Println("************************************************************************************************")
+
+			return installFile(install, filepath.Join(dest, DataDir, install.Version), file)
+		}
 	}
 
 	// Ensure directory exists