diff --git a/QtPMbrowser/pmbrowserwindow.cpp b/QtPMbrowser/pmbrowserwindow.cpp
index 843b68e..04f3fde 100644
--- a/QtPMbrowser/pmbrowserwindow.cpp
+++ b/QtPMbrowser/pmbrowserwindow.cpp
@@ -36,6 +36,7 @@
 #include <QTableView>
 #include <string>
 #include <fstream>
+#include <filesystem>
 #include <iostream>
 #include <ctime>
 #include <cstring>
@@ -306,10 +307,46 @@ void PMbrowserWindow::loadFile(QString filename)
         datfile->InitFromStream(infile);
     }
     catch (const std::exception& e) {
-        QMessageBox::warning(this, QString("File Error"), 
-            QString("error while processing dat file:\n") + QString(e.what()));
+        //QMessageBox::warning(this, QString("File Error"), 
+        //    QString("error while processing dat file:\n") + QString(e.what()));
+		qDebug() << e.what();
         datfile = nullptr;
-        infile.close();
+        infile.seekg(0, std::ios_base::beg);
+        //infile.close();
+    }
+    if (!datfile) {
+        try {
+            // we might habe an unbundled dat file
+            datfile = std::make_unique<DatFile>();
+            std::filesystem::path path(QFile::encodeName(filename).constData());
+            path.replace_extension(hkLib::ExtPul);
+            std::ifstream pulstream(path, std::ios_base::binary | std::ios_base::in);
+            if (!pulstream) {
+                throw std::runtime_error(std::string("could not open pul file, ") + ::strerror(errno));
+            }
+            auto pullength = std::filesystem::file_size(path);
+            path.replace_extension(hkLib::ExtPgf);
+            std::ifstream pgfstream(path, std::ios_base::binary | std::ios_base::in);
+            if (!pgfstream) {
+                throw std::runtime_error(std::string("could not open pgf file, ") + ::strerror(errno));
+            }
+            auto pgflength = std::filesystem::file_size(path);
+            path.replace_extension(hkLib::ExtAmp);
+            std::ifstream ampstream(path, std::ios_base::binary | std::ios_base::in);
+            if (!ampstream) {
+                datfile->InitFromStream(infile, pulstream, pullength, pgfstream, pgflength, nullptr, 0);
+            }
+            else {
+                datfile->InitFromStream(infile, pulstream, pullength, pgfstream, pgflength, &ampstream, std::filesystem::file_size(path));
+            }
+        }
+        catch (const std::exception& e) {
+            qDebug() << e.what();
+            QMessageBox::warning(this, QString("File Error"),
+                QString("error while processing unbundled dat file:\n") + QString(e.what()));
+            datfile = nullptr;
+            infile.close();
+        }
     }
     if(datfile) {
         populateTreeView();
diff --git a/hekatoolslib/DatFile.cpp b/hekatoolslib/DatFile.cpp
index ece092a..f389f78 100644
--- a/hekatoolslib/DatFile.cpp
+++ b/hekatoolslib/DatFile.cpp
@@ -105,6 +105,41 @@ void DatFile::InitFromStream(std::istream& infile)
     if (!PgfTree.isValid())throw std::runtime_error("no valid Pgf in file");
 }
 
+void hkLib::DatFile::InitFromStream(std::istream& infile, std::istream& pulstream, std::uintmax_t pullength, std::istream& pgfstream,
+    std::uintmax_t pgflength, std::istream* ampstream, std::uintmax_t amplength)
+{
+    if (!infile) {
+        throw std::runtime_error("cannot access file");
+    }
+    auto bh = std::make_unique<BundleHeader>();
+    infile.read(reinterpret_cast<char*>(bh.get()), BundleHeaderSize);
+    if (!infile) {
+        throw std::runtime_error("cannot read file");
+    }
+
+    bool has_header = std::memcmp(bh->Signature, BundleSignatureInvalid, 8) == 0;
+    // Note: if it has a valid signature, it should not be handeled by this function
+    if (has_header) {
+        Version = bh->Version;
+        Time = bh->Time;
+        isSwapped = bool(bh->IsLittleEndian) != MachineIsLittleEndian();
+        if (isSwapped) {
+            swapInPlace(Time);
+        }
+    }
+    if(!PulTree.InitFromStream(ExtPul, pulstream, 0, static_cast<unsigned int>(pullength))){
+        throw std::runtime_error("error processing pulse tree");
+	}
+    if (!PgfTree.InitFromStream(ExtPgf, pgfstream, 0, static_cast<unsigned int>(pgflength))) {
+        throw std::runtime_error("error processing pgf tree");
+    }
+    if (ampstream && amplength) {
+        if (!AmpTree.InitFromStream(ExtAmp, *ampstream, 0, static_cast<unsigned int>(amplength))) {
+            throw std::runtime_error("error processing amp tree");
+		}
+    }
+}
+
 std::string DatFile::getFileDate() const
 {
 #ifndef NDEBUG
diff --git a/hekatoolslib/DatFile.h b/hekatoolslib/DatFile.h
index e987990..62c34cd 100644
--- a/hekatoolslib/DatFile.h
+++ b/hekatoolslib/DatFile.h
@@ -78,7 +78,24 @@ namespace hkLib {
 			PgfTree{}, AmpTree{} {};
 		DatFile(const DatFile&) = delete;
 		DatFile operator=(const DatFile&) = delete;
-		void InitFromStream(std::istream& istream);
+		/// <summary>
+		/// initialize from bundle file stream, reads header and tree data, but not raw data
+		/// </summary>
+		/// <param name="istream">input stream of the bundle file</param>
+		void InitFromStream(std::istream& infile);
+		/// <summary>
+		/// initialized from unbundles dat file, requires separate streams for each tree, and their lengths
+		/// </summary>
+		/// <param name="infile">dat file stream</param>
+		/// <param name="pulstream">pul file stream</param>
+		/// <param name="pullength">length of pul file</param>
+		/// <param name="pgfstream">pgf file stream</param>
+		/// <param name="pgflength">length of pgf file</param>
+		/// <param name="ampstream">pointer to optional amp file stream, can be nullptr</param>
+		/// <param name="amplength"length of amp file, 0 if no amp file</param>
+		void InitFromStream(std::istream& infile, std::istream& pulstream, std::uintmax_t pullength,
+			std::istream& pgfstream, std::uintmax_t pgflength,
+			std::istream* ampstream, std::uintmax_t amplength);
 		std::string getFileDate() const; // return formatted file creation date
 		hkTree& GetPulTree() { return PulTree; };
 		hkTree& GetPgfTree() { return PgfTree; };