There are many reasons you might want to download Windows 7. For example, if you need to install Windows 7 but you've lost your original setup disc, or it's damaged, downloading Windows 7 would get you out of that bind.
Computer makers also often don't include a Windows 7 DVD with new computers, complicating the process of a Windows 7 clean install and even some advanced troubleshooting that typically requires a Windows 7 disc.
You might also might want to download Windows 7 just to try out the operating system or to put it on a second computer at home. Windows can be expensive so finding a place to download Windows 7 for free is an enticing thought. Pretty much everything is available on the Internet for free, right?
It's important to realize that in many ways, what you actually pay for when you legally purchase a copy of Windows 7 is the product key, sometimes referred to as a CD key or key code, or incorrectly as the serial number. This unique number is required to be able to fully use Windows 7. So even if you did download Windows 7 without paying for it, you would still need a valid Windows 7 product key.
Note: If you actually do have a Windows 7 DVD but you've lost your product key, there may be a way to find it. See How To Find the Windows 7 Product Key for some help.
Download Windows 7 the 100% Legal Way
There are actually three ways to download Windows 7 legally but they each have a caveat that you're probably not going to like.
Your first option is a free download of Windows 7 Enterprise. Unfortunately, it's only a 90-day trial after which time your computer will shut down every hour. This Windows 7 download is intended for testing by software and hardware developers and isn't a good long-term solution.
Your second and third options are to download Windows 7 for "free" as part of your paid TechNet Subscription or MSDN Subscription. These professional subscriptions by Microsoft grant you access to Windows 7 downloads and product keys, as well as software and keys for most of the software Microsoft produces. Unless you're an IT professional, these subscriptions probably aren't cost effective ways to get your hands on a Windows 7 download.
Note: Prior to late 2012, Windows 7 was available for individuals to purchase and download directly from the Microsoft Store. While this is still an option for Windows 8, it is, unfortunately, no longer possible for Windows 7.
Of course if downloading Windows 7 isn't necessary in your situation, your other option is to purchase a copy of Window 7 on DVD [Check Prices].
That's it. So yes, all reasonable legal options require paying, either for a DVD in a retail package, or for a download via a professional subscription, in ISO format, for burning to a disc or transfer to a USB device.
Note: If you have a Windows 7 disc, and are only trying to download Windows 7 because you need to install it on your computer which does not have an optical drive, there is a way to get the installation files from your DVD onto a flash drive. See How To Install Windows 7 From USB for instructions.
The "Digital River" Method
Back when Windows 7 was available for purchase and download through the Microsoft Store, Microsoft used a company by the name of Digital River to provide the Windows 7 ISO images. As of this writing, those Windows 7 ISO files are on a public, unsecured server and can be downloaded without showing any proof of purchase.
This may be a long-running mistake on the part of Digital River, or perhaps Microsoft simply doesn't mind considering the fact that you need a valid product key to use Windows 7 for more than 30 days anyway. I've reached out to Microsoft for comment but I've yet to receive anything on the matter. I'll update this page when/if I hear from them.
Chances are these Windows 7 ISO files shouldn't be so easily available. So, for the time being, I don't feel comfortable linking directly to the Windows 7 downloads on Digital River's servers. You can do your own search for them if you like.
Other Windows 7 Downloads
Any other "free" Windows 7 download you come across online is most certainly illegal, including Windows 7 ISO files obtained via torrents or directly from other websites or servers. Aside from legal issues, these Windows 7 downloads, unlike the official ones from Digital River, run the risk of being something other than advertised.
For example, many Windows 7 images available on torrent sites and from other unofficial sources are "cracked" versions of Windows 7, meaning they've been modified for various reasons... and may also include built-in malware. Best to avoid a situation like that.
Don't Download Windows 7: Replace It
A final option for those of you with broken or lost Windows 7 discs: try to get a replacement Windows 7 disc instead of taking unnecessary risks with a Windows 7 download.
If Windows 7 came preinstalled on your computer, and you did have a disc but it's now lost or damaged, contact your computer maker for a replacement. Depending on your computer maker's policy, the replacement Windows 7 media may be free or you may be charged a small fee.
If you're in a similar situation with a Windows 7 disc but you purchased a retail copy of Windows 7 on DVD, or you legitimately purchased and downloaded Windows 7 from Microsoft, you can contact the Microsoft Supplemental Parts team and request a replacement. You can find their contact information here.
Finally, while not a replacement for Windows 7, you should know that it's possible to create a system repair disc for Windows 7 from any other Windows 7 computer, including a friend's, for just the cost of a blank CD. That disc can be used to perform all the diagnostic and repair functions that a full Windows 7 setup DVD can. See How To Create a Windows 7 System Repair Disc for instructions.