The bug is triggered when both the sector with address n and the sector with address n+128GiB is written. Old LBA is 28-bit and can address 128 GiB only, it means that if you try to write address on position 128GiB + 1, the first sector of the HDD is written. This behavior is not related to partition size or data size, but if you have the first partition 128 GiB, then even few bytes in the beginning of the second partition can overwrite some data in the second partition. And what may happen? It depends on the fact what you will overwrite. If partition tavble, boot records, file allocation tables or directory entries are overwritten, then the HDD may become unaccessible or scandisk can find the errors. But if just some data are overwritten, scandisk will show no error and the only possibility to detect is to compare original and copied files. Petr Thanks for clarifying. This means my last test would have been sufficient. In any event, I have now filled the entire drive and rebooted/scandisked. It's quite apparent that this fix works exactly as intended. I hope no one asks me to keep filling it