diff --git a/Device/DiskCopy42Image.cpp b/Device/DiskCopy42Image.cpp
index 7c0956c..9498720 100644
--- a/Device/DiskCopy42Image.cpp
+++ b/Device/DiskCopy42Image.cpp
@@ -170,41 +170,38 @@ BlockDevicePointer DiskCopy42Image::Create(const char *name, size_t blocks, cons
     return MAKE_SHARED(DiskCopy42Image, file);
 }
 
-void DiskCopy42Image::Validate(MappedFile *file)
+bool DiskCopy42Image::Validate(MappedFile *file, const std::nothrow_t &)
 {
 #undef __METHOD__
 #define __METHOD__ "DiskCopy42Image::Validate"
-
+    
+    
     size_t bytes = 0;
     size_t size = file->length();
     const void *data = file->address();
-    bool ok = false;
     uint32_t checksum = 0;
     
-    do {
-        if (size < oUserData) break;
-        
-        // name must be < 64
-        if (Read8(data, 0) > 63) break;
-        
-        if (Read16(data, oPrivate) != 0x100)
-            break;
-        
-        // bytes, not blocks.
-        bytes = Read32(data, oDataSize);
-        
-        if (bytes % 512) break;
-        
-        if (size < oUserData + bytes) break;
-        
-        // todo -- checksum.
-        checksum = Read32(data, oDataChecksum);
-        
-        ok = true;
-    } while (false);
+    if (size < oUserData) 
+        return false;
     
-    if (!ok)
-        throw Exception(__METHOD__ ": Invalid file format.");
+    // name must be < 64
+    if (Read8(data, 0) > 63) 
+        return false;
+    
+    if (Read16(data, oPrivate) != 0x100)
+        return false;
+    
+    // bytes, not blocks.
+    bytes = Read32(data, oDataSize);
+    
+    if (bytes % 512) 
+        return false;
+    
+    if (size < oUserData + bytes) 
+        return false;
+    
+    // todo -- checksum.
+    checksum = Read32(data, oDataChecksum);
     
     uint32_t cs = Checksum(oUserData + (uint8_t *)data, bytes);
     
@@ -212,7 +209,21 @@ void DiskCopy42Image::Validate(MappedFile *file)
     {
         fprintf(stderr, __METHOD__ ": Warning: checksum invalid.\n");
     }
+    
+    return true;
+}
 
+
+bool DiskCopy42Image::Validate(MappedFile *file)
+{
+#undef __METHOD__
+#define __METHOD__ "DiskCopy42Image::Validate"
+
+
+    if (!Validate(file, std::nothrow))
+        throw Exception(__METHOD__ ": Invalid file format.");
+    
+    return true;
 }
 
 void DiskCopy42Image::write(unsigned block, const void *bp)
diff --git a/Device/DiskCopy42Image.h b/Device/DiskCopy42Image.h
index df5c95f..a165b1a 100644
--- a/Device/DiskCopy42Image.h
+++ b/Device/DiskCopy42Image.h
@@ -19,6 +19,11 @@ public:
 
     static uint32_t Checksum(void *data, size_t size);
 
+    static bool Validate(MappedFile *, const std::nothrow_t &);
+    static bool Validate(MappedFile *);
+    
+    
+    
     virtual void write(unsigned block, const void *bp);
     
 
@@ -29,7 +34,6 @@ private:
     DiskCopy42Image();
 
     DiskCopy42Image(MappedFile *);
-    static void Validate(MappedFile *);
     bool _changed;
 };
 
diff --git a/Device/DiskImage.cpp b/Device/DiskImage.cpp
index 2450ccb..a1c15b9 100644
--- a/Device/DiskImage.cpp
+++ b/Device/DiskImage.cpp
@@ -149,7 +149,7 @@ bool ProDOSOrderDiskImage::Validate(MappedFile *f)
     
     if (!f || !f->isValid()) throw Exception(__METHOD__ ": File not set.");
 
-    if (!Validate(f))
+    if (!Validate(f, std::nothrow))
         throw Exception(__METHOD__ ": Invalid file format.");
     
     return true;
@@ -221,7 +221,7 @@ bool DOSOrderDiskImage::Validate(MappedFile *f)
     if (!f || !f->isValid()) throw Exception(__METHOD__ ": File not set.");
     
     
-    if (!Validate(f))
+    if (!Validate(f, std::nothrow))
         throw Exception(__METHOD__ ": Invalid file format.");
     
     return true;
diff --git a/Device/SDKImage.cpp b/Device/SDKImage.cpp
index eb62279..58c7772 100644
--- a/Device/SDKImage.cpp
+++ b/Device/SDKImage.cpp
@@ -226,7 +226,7 @@ bool SDKImage::Validate(MappedFile * f)
 #undef __METHOD__
 #define __METHOD__ "SDKImage::Validate"
     
-    if (!Validate(f))
+    if (!Validate(f, std::nothrow))
         throw Exception(__METHOD__ ": Invalid file format.");
 
     return true;