Quite right. Or you can look here. You can download Windows 7 from Softpedia, a large and well-known freeware, shareware, and trialware download site. Because Windows 7 is not free, and it's certainly not shareware, this qualifies as a "trial". Without a product key, you can use it for something like 30 days before Windows cripples itself.
As Ignatzatsonic has pointed out you can also download at "mydigitallife.info" that includes direct links to the various Windows 7 .iso files hosted at Digital River. Digital River is a well-known and trusted service provider for companies large and small selling software.
Make sure to select the correct edition - Home Premium, Pro, Ultimate or Enterprise - and processor type - 32-bit (x86) or 64-bit(labeled x64). Of course, Windows 7 is available from many other places, including assorted file sharing sites and peer-to-peer networks. Those are clearly not sanctioned and often include additional whammies in the form of various malware.
Regardless of where you get it from, please make absolutely certain that you're getting it from a trusted source. Right now, I think both Softpedia and mydigitallife.info are the best. Hopefully you have the original product key tucked away somewhere.