Thanks for your response Saltgrass.
Yes, I think you are correct. When the Linux bootloader was written to the Windows drive (by accident), it overwrote part of the partition table.
I ran a check with a tool called Testdisk, and it shows that there is a partition that was deleted, but it can't recover it.
Unfortunately I did not make the Recovery Disks before this happened.
For now, I have Windows 7 working properly, but I would like to reset it to factory default.
I have just ordered the Recovery Media from Gateway (Acer). That will solve my whole issue.
Thanks again.