Hello fellow Mac users, I recently replaced the 250GB stock hard disk in my unibody MBP with a 500GB Seagate disk (ST9500420AS). All data was moved from the old to the new disk using a the most recent Time Machine backup. One evening about a week later, MacOS started running extremely slow, to the point where it would take several minutes for basic tasks like opening a context menu etc. to be carried out. Rebooting did not resolve this issue and after a few further reboots MacOS would not boot anymore. Disk Utility reported "Invalid Node Structure" and was unable to repair the disk. Disk Warrior was able to restore all the data on the disk (not really a concern as I have the backups) but could not repair it either. As I had changed the partitioning of the drive a day or two before that (using GParted and rEFIt; to expand the Windows partition), I thought that this might be the problem and re-imaged the disk from my Time Machine backup with the desired partitioning already in place. 3 days later I am in the same situation again... Now before I go and spend hours setting up the system from scratch, I would like to rule out hardware issues. Sadly Seagate's own SeaTools (for DOS) utility does not work on current Macs as it requires a PS/2 mouse and keyboard to be present (via hardware or BIOS emulation; neither of which is in a Mac these days). SeaTools for Windows runs from my Windows installation but quits any tests I run after a few seconds with a simple "FAIL" message. Hence my question: Are there any freeware tools for the Mac that would allow me to determine the health status of the hard disk? A Google search only returns commercial products. Or should I return the disk for a replacement? Thanks!