If I read your post correctly, you want to restore the laptop to the original Acer configuration, with Windows 7 only. If that is correct, then you have a few options.
It sounds like the recovery DVD is expecting one particular partition table configuration on the hard disk, which was altered by the Ubuntu installation.
Does the Acer recovery DVD allow you to alter the partitions? If so, delete all partitions and then perform the full recovery.
If not, you can reboot the Ubuntu CD, proceed with the installation until you get the hard disk partition options, then manually delete all the partitions. Without proceeding any further, reboot the laptop, and insert the Acer recovery DVD, and perform the recovery.