diff --git "a/sdk/lib/fslib/vfatlib/check/fat.c" "b/sdk/lib/fslib/vfatlib/check/fat.c"
index efb05e1cdb7..af632ebf6bc 100644
--- "a/sdk/lib/fslib/vfatlib/check/fat.c"
+++ "b/sdk/lib/fslib/vfatlib/check/fat.c"
@@ -118,11 +118,21 @@ void read_fat(DOS_FS * fs)
 	second_ok = (second_media.value & FAT_EXTD(fs)) == FAT_EXTD(fs);
 	if (first_ok && !second_ok) {
 	    printf("FATs differ - using first FAT.\n");
+#ifdef __REACTOS__
+        if (rw)
+	        fs_write(fs->fat_start + fs->fat_size, eff_size, first);
+#else
 	    fs_write(fs->fat_start + fs->fat_size, eff_size, first);
+#endif
 	}
 	if (!first_ok && second_ok) {
 	    printf("FATs differ - using second FAT.\n");
+#ifdef __REACTOS__
+        if (rw)
+            fs_write(fs->fat_start, eff_size, second);
+#else
 	    fs_write(fs->fat_start, eff_size, second);
+#endif
 	    memcpy(first, second, eff_size);
 	}
 	if (first_ok && second_ok) {
@@ -130,15 +140,30 @@ void read_fat(DOS_FS * fs)
 		printf("FATs differ but appear to be intact. Use which FAT ?\n"
 		       "1) Use first FAT\n2) Use second FAT\n");
 		if (get_key("12", "?") == '1') {
+#ifdef __REACTOS__
+            if (rw)
+		       fs_write(fs->fat_start + fs->fat_size, eff_size, first);
+#else
 		    fs_write(fs->fat_start + fs->fat_size, eff_size, first);
+#endif
 		} else {
+#ifdef __REACTOS__
+            if (rw)
+		        fs_write(fs->fat_start, eff_size, second);
+#else
 		    fs_write(fs->fat_start, eff_size, second);
+#endif
 		    memcpy(first, second, eff_size);
 		}
 	    } else {
 		printf("FATs differ but appear to be intact. Using first "
 		       "FAT.\n");
+#ifdef __REACTOS__
+        if (rw)
+		    fs_write(fs->fat_start + fs->fat_size, eff_size, first);
+#else
 		fs_write(fs->fat_start + fs->fat_size, eff_size, first);
+#endif
 	    }
 	}
 	if (!first_ok && !second_ok) {
@@ -249,7 +274,18 @@ void set_fat(DOS_FS * fs, uint32_t cluster, int32_t new)
     default:
 	die("Bad FAT entry size: %d bits.", fs->fat_bits);
     }
+#ifdef __REACTOS__
+    if (rw)
+    {
+        fs_write(offs, size, data);
+        if (fs->nfats > 1)
+        {
+	        fs_write(offs + fs->fat_size, size, data);
+        }
+    }
+#else
     fs_write(offs, size, data);
+#endif
     if (fs->nfats > 1) {
 	fs_write(offs + fs->fat_size, size, data);
     }
@@ -514,7 +550,12 @@ void reclaim_file(DOS_FS * fs)
 		de.size = htole32(le32toh(de.size) + fs->cluster_size);
 		reclaimed++;
 	    }
+#ifdef __REACTOS__
+        if (rw)
+	        fs_write(offset, sizeof(DIR_ENT), &de);
+#else
 	    fs_write(offset, sizeof(DIR_ENT), &de);
+#endif
 	}
     if (reclaimed)
 	printf("Reclaimed %d unused cluster%s (%llu bytes) in %d chain%s.\n",
@@ -580,8 +621,14 @@ uint32_t update_free(DOS_FS * fs)
     if (do_set) {
 	uint32_t le_free = htole32(free);
 	fs->free_clusters = free;
+#ifdef __REACTOS__
+    if (rw)
+	    fs_write(fs->fsinfo_start + offsetof(struct info_sector, free_clusters),
+            sizeof(le_free), &le_free);
+#else
 	fs_write(fs->fsinfo_start + offsetof(struct info_sector, free_clusters),
 		 sizeof(le_free), &le_free);
+#endif
     }
 
     return free;