diff --git a/CMakeLists.txt b/CMakeLists.txt
index 63306b7be2..21bf134685 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -77,4 +77,5 @@ add_subdirectory(ConvertObj)
 add_subdirectory(PEFTools)
 add_subdirectory(Elf2Mac)
 add_subdirectory(LaunchAPPL)
+add_subdirectory(ConvertDiskImage)
 endif()
diff --git a/ConvertDiskImage/CMakeLists.txt b/ConvertDiskImage/CMakeLists.txt
new file mode 100644
index 0000000000..0665b42f38
--- /dev/null
+++ b/ConvertDiskImage/CMakeLists.txt
@@ -0,0 +1,2 @@
+add_executable(ConvertDiskImage ConvertDiskImage.cc)
+target_link_libraries(ConvertDiskImage ResourceFiles)
diff --git a/ConvertDiskImage/ConvertDiskImage.cc b/ConvertDiskImage/ConvertDiskImage.cc
new file mode 100644
index 0000000000..584a56af30
--- /dev/null
+++ b/ConvertDiskImage/ConvertDiskImage.cc
@@ -0,0 +1,130 @@
+#include <ResourceFile.h>
+#include <BinaryIO.h>
+#include <iostream>
+#include <sstream>
+#include <fstream>
+#include <cassert>
+#include <vector>
+
+void decompreassADC(std::vector<uint8_t>& outbuf, const std::vector<uint8_t>& inbuf)
+{
+    outbuf.reserve(0x40000);
+    auto p = inbuf.begin();
+
+    while(p != inbuf.end())
+    {
+        auto cmd = *p++;
+        if(cmd & 0x80)
+        {
+            int n = (cmd & 0x7f) + 1;
+            outbuf.insert(outbuf.end(), p, p + n);
+            p += n;
+        }
+        else
+        {
+            int off;
+            int n;
+            if(cmd & 0x40)
+            {
+                n = (cmd & 0x3f) + 4;
+                off = *p++ << 8;
+                off |= *p++;
+            }
+            else
+            {
+                n = ((cmd & 0x3c) >> 2) + 3;
+                off = ((cmd & 3) << 8) | *p++;
+            }
+            ++off;
+            
+            outbuf.reserve(outbuf.size() + n);
+            outbuf.insert(outbuf.end(), outbuf.end() - off, outbuf.end() - off + n);
+        }
+    }
+}
+
+int main(int argc, char* argv[])
+{
+    if(argc != 3)
+	{
+		std::cerr << "Usage: ConvertDiskImage input.img output.dsk\n";
+		return 1;
+	}
+
+    ResourceFile file(argv[1]);
+    if(!file.read())
+    {
+        std::cerr << "Couldn't read input.\n";
+        return 1;
+    }
+
+    std::istringstream bcem(file.resources.resources[ResRef("bcem",128)].getData());
+    std::istringstream ndif(file.data);
+    std::ofstream output(argv[2], std::ios::binary | std::ios::trunc);
+
+    word(bcem);
+    word(bcem);
+    for(int i = 0; i<64; i++)
+        byte(bcem); // volume name
+    
+    int blockCount [[maybe_unused]] = longword(bcem);
+    int blockSize = longword(bcem) & ~1; // ???
+    std::cout << blockCount << " blocks of " << blockSize << std::endl;
+    int hhBSZeroOffset [[maybe_unused]] = longword(bcem);
+    int checksum [[maybe_unused]] = longword(bcem);
+    int unknown1 [[maybe_unused]] = longword(bcem);
+    int unknown2 [[maybe_unused]] = longword(bcem);
+    int unknown3 [[maybe_unused]] = longword(bcem);
+
+    for(int i = 0; i < 7; i++)
+        longword(bcem); // reserved
+
+    int nChunks = longword(bcem);
+
+    std::vector<uint8_t> inbuf;
+    std::vector<uint8_t> outbuf;
+
+    for(int i = 0; i < nChunks; i++)
+    {
+        unsigned tmp = longword(bcem);
+        unsigned dstStartOffset = blockSize * (tmp >> 8);
+        unsigned compression = tmp & 0xFF;
+        unsigned offset = longword(bcem);
+        unsigned size = longword(bcem);
+
+        std::cout << std::hex << "starting at " << dstStartOffset << " from " << offset << " size " << size << " compression " << compression << std::endl;
+
+        if(output.tellp() < dstStartOffset)
+        {
+            std::cout << std::hex << "zero bytes from " << output.tellp() << std::endl;
+
+            output.seekp(dstStartOffset - 1);
+            output.put(0);
+        }
+
+        inbuf.clear();
+        outbuf.clear();
+
+        inbuf.resize(size);
+        ndif.seekg(offset);
+        ndif.read((char*)inbuf.data(), size);
+
+        switch(compression)
+        {
+            case 0:
+            case 0xFF:
+                break;
+            case 2:
+                outbuf = std::move(inbuf);
+                break;
+            
+            case 0x83:
+                decompreassADC(outbuf, inbuf);
+                break;
+        }
+
+        output.write((char*)outbuf.data(), outbuf.size());
+    }
+
+    return 0;
+}