It is possible. When I installed as non-Admin on my XP machines, the installer would ask if i wanted just for me (I did) or for all (where it needed an admin passwd).

Installing Cygwin. To do that, open up your Start menu, type “system” and select the option “System” in the control panel section. If you are using Windows 8, you can access the same section by pressing “Win + X” and selecting “System” from the power user menu.

It can go anywhere on disk (though I'd recommend a folder without spaces in it, since many scripts don't guard against spaces in filepaths) and doesn't have much in the way of registry entries in base install. Some tools like inetd, sshd, and cron will need admin to install the services, but these are less critical.

That said, I haven't tested on Win7 (I now have a Linux desktop, don't need Cygwin). As someone else said, be careful if you're not authorized for this. There are a lot of tools in corporate environments that look for rogue installs of software. Abl80 flex operator's manual. You'll be installing a huge heap of EXEs for them to find.