I have an SSD in my laptop that has elementaryOS installed to it, I want to uninstall elementaryOS so I can install Windows 7.
Insert your W7 ISO CD/USB, boot from it, when you see the "install windows7" sign, press SHIFT+10. That will open command prompt windows. Now, type the following.
diskpart > list > select disk 0 > clean (one by one) Once the operation completed, you can close cmd window, and can continue with the w7 installation process. What it does is it formats the entire disk in ext format to FAT format. Windows cannot read ext format. Remember that this operation will completely wipe your disk. Hope my answer helps you. :)