The OS has no control over what sector size the hard drive uses. The only way to switch back and forth is with a utility that can tell the drive what sector size to use. Using 4k sectors is the only way to create partitions greater than 2TB in XP.
For the 3TB drive, you need to use the Quick Formatter. I don’t think the Advanced Format Utility handles 3TB drives correctly. I’ll look into it to find out for sure.
