Last week I ran a chkdsk /r on a half-full, single partition 3.5-inch 500gb 7200rpm external hard drive (32mb cache), and it took 4 or 5 hours to complete. No problems were found. Today I ran a full format on new, single-partition 2.5-inch 500gb 7200rpm external drive (16mb cache), and it only took about 20 minutes. Any idea why there would be such a huge completion-time discrepancy? My understanding was that full format looks for bad sectors just like (the time-consuming part of) chkdsk /r. I’m using Windows XP-SP3, and both drives are in external enclosures connected by USB 2.0. They seem to have similar file transfer rates. Thanks.