Be sure not to use illegal copy of windows, you can download evaluation version of Windows bootable ISO from Microsoft download site.
S Anand Kumar
You could also risk the wrath of Microsoft and follow the instructions here to create a bootable disk. It’s pretty easy if you have Nero or a similar program, but I wouldn’t recommend using their built-in cd images.
There’s also a program out there that can do this for you but I can’t seem to find it at this point.
Also you will need a product key for the installer which you can probably get from your friend.
Another option is to get a TechNet or an MSDN subscription. either one will allow you to download bootable ISO images of pretty much everything that Microsoft makes (aside from games and other consumer products).