On my 3750, regions 45, 76, 139 to 143 are filled with FF only. Maybe try an erase on them? Make backups first!
Careful! We are in uncharted territory here.
Edit: region 76 seems to be empty on 3450 (0 byte in size).
After disaster when modifying region 41 I will wait for a while. Maybe there is a safer solution to recover HWID.
Maybe somebody know why I lost HWID. Maybe I modified somehow protected region 41 area?
Bookmarks