Hi,
if you can get a copy of Windows 7 SP1 then future trouble shooting will be far easier.
If you know the activation key and depending on what type of licence you have then you can access the official Windows 7 iso's here:
Download Windows 7 Disc Images (ISO Files)
I have a sneaking suspicion however that your copy of Windows is probably OEM (basically this means the licence is tied to the machine/motherboard and is non transferable)
This site will point you in the right direction in regards to getting a Windows 7 iso (I do not condone the use of pirate material and neither does this website but if it's simply for troubleshooting use then why not?):
Every Way to Download Windows 7 ISOs, Legally and for Free | PCsteps.com
Once you have your copy of Windows 7 SP1 post back and we'll guide you through a system repair..