Index: tol/btol/vmatrix_type/vmat_io.cpp
===================================================================
--- tol/btol/vmatrix_type/vmat_io.cpp	(revision 3e2cc31846d6dcecf18c2fe999691fe67353f4f5)
+++ tol/btol/vmatrix_type/vmat_io.cpp	(revision 53ed3a0ee15ba6399186beaa3735de86c2a4b3bd)
@@ -193,7 +193,13 @@
         I2("virtual matrix","")+" "+CodeName(a.code_)+
            "("+a.Rows()+"x"+a.Columns()+")"+" ");
+#if defined( WIN32 )
+  FILE *f = fopen("c:\\fail_chol.mtx", "w");
+#else
   FILE *f = fopen("/tmp/fail_chol.mtx", "w");
-  ((BVMat&)a).WriteMatrixMarket(f);
-  fclose(f);
+#endif
+  if ( f ) {
+    ((BVMat&)a).WriteMatrixMarket(f);
+    fclose(f);
+  }
 }