Just download Win7 from a torrent site, install daemon Tools (lite), mount the iso => After the windows installation, download an Activator, and you have a legal windows 7 + All the updates
But if your laptop is to slow, make a bootable USB with the iso on another computer. Install it on your laptop and download the activator.
Price is 0$ And you get all the important + bullshit updates from M$

If you prefer the legal way go ahead, but if you want a special activator, tell me, and I'll upload it, because I had to search a long time to find a good one.
I have my WIn 7 for almost a year and it's still acting as a legal windows :p