Hi, I had a look around but couldn't find advice which matches my case. I have an Intel IMac a few years old, which recently started to freeze frequently. I checked the logs and found suspicious disk errors. Indeed running disk utility reveals problems ("invalid sibling link"). I have run disk utility from the CD but it seems unable to repair this problem: What should I do next? It seems I have the following options: 1. run fsck. However the Apple documentation suggests that this is only useful if you cannot run the disk utility. 2. run another tool. There seem to be a number of them around. Which one is any good? I may spend money but the tool is unable to fix my disk. 3. reformat the hard disk. I seem to able to copy my files but this certainly takes up some time reinstalling everything. 4. replace the hard disk. Obviously this also would entail 3. I guess I'd only do this if it turns out that there is actually a hardware problem with the disk. Any advice is appreciated.