diff --git a/src/calibre/__init__.py b/src/calibre/__init__.py
index e619d00a31..b4e347a9af 100644
--- a/src/calibre/__init__.py
+++ b/src/calibre/__init__.py
@@ -409,8 +409,8 @@ def relpath(target, base=os.curdir):
     target_list = (os.path.abspath(target)).split(os.sep)
 
     # On the windows platform the target may be on a completely different drive from the base.
-    if iswindows and base_list[0] != target_list[0]:
-        raise OSError, 'Target is on a different drive to base. Target: '+target_list[0].upper()+', base: '+base_list[0].upper()
+    if iswindows and base_list[0].upper() != target_list[0].upper():
+        raise OSError, 'Target is on a different drive to base. Target: '+repr(target)+', base: '+repr(base)
 
     # Starting from the filepath root, work out how much of the filepath is
     # shared by base and target.
diff --git a/src/calibre/ebooks/metadata/__init__.py b/src/calibre/ebooks/metadata/__init__.py
index eacc4f04e0..7807c66a86 100644
--- a/src/calibre/ebooks/metadata/__init__.py
+++ b/src/calibre/ebooks/metadata/__init__.py
@@ -83,7 +83,10 @@ class Resource(object):
         frag = '#'+quote(self.fragment) if self.fragment else ''
         if self.path == basedir:
             return ''+frag
-        rpath = relpath(self.path, basedir)
+        try:
+            rpath = relpath(self.path, basedir)
+        except OSError: # On windows path and basedir could be on different drives
+            rpath = self.path
         
         return quote(rpath.replace(os.sep, '/'))+frag