Hello Furhead, when using a removable USB device, if other USB devices were added or removed the device with your backups may have been assigned a different drive letter. To check the drive letter assigned to the memory stick insert it into your laptop, open Computer and view the letter assigned to the removable storage device. If One Care backup for example says it can't locate E:\ One Care Backup and in Computer the device is listed as F:\, change the drive letter to E:\. It is also possible that the 4g memory stick does not have enough free space to perform another backup.