I have heard from my friends that Ubuntu would be good, but I can pray like Windows 7 Enterprise. So how do I get Eindows 7 Enterprise back?
Hello, you would need an installation CD/DVD and installing the operating system from scratch. Here is a link explaining how:
try to get window 7 boot-able cd, insert it into the computer and boot your computer from cd
Assuming you installed Ubuntu over Windows, you'll have to re-install it. You can probably use your old Windows disk and product key, so just place your Windows 7 disk in the drive, reboot your computer, and follow the instructions. Make sure you back up everything you want to save, since you'll most likely be installing over Ubuntu you will lose all data residing in that operating system. Or you could setup a second partition and dual boot, but that's a pain if you're installing windows after Ubuntu.
You need a bootable windows 7 installation disk or usb drive. And install a fresh copy of windows, You can keep ubuntu if you like by installing ubuntu inside windows.
If you replaced the entire operating system (contents of the hard disk) during the ubuntu installation you will have to re-install Windows 7 using the installation DVD or a USB flash drive.
If you installed Ubuntu in a dual-boot you can remove it using the following guide on safely uninstall Ubuntu.