Backup using Winzip spanning across zip

Attempting to backup a directory 850mb to zip disks. When it gets to the point of changing the disks from disk 1 to disk 2, the zip drive will not eject the disk. I then attemped to manually eject using the software from explorer (which does in fact eject the disk). The problem is that that a blue screen of death appears saying that the drive was still in use (but the light indicating read/write on the drive is no longer blinking). The only way to recover is hard-boot. Any suggestions on how to have the disk eject, and continue on with the backup.