Quote - New browsers support new Web technologies (like HTML5 and CSS3). These languages serve as a foundation for many websites today, and for virtually all new websites and Web apps. But unfortunately, many of these new websites will neither look nor function in the same way in old browsers like IE8. Also, jQuery v2, the major javascript framework, no longer supports IE6, 7 & 8. If you’re on a system at your place of employment where you’re not able to upgrade or download a new browser,  Chrome Frame is a viable option. You don’t need any special administrator privileges to install Chrome Frame, so you can keep using the same version of Internet Explorer, and almost instantly have a far superior browsing experience that’s identical to using the latest version of Google Chrome.

I'd like to make a few points regarding the above.

I don't advise Chrome Frame, because Google itself is/has discontinued support for it.

http://blog.chromium.org/2013/06/retiring-chrome-frame.html

And while I agree that older clients don't support some of the features of newer ones, tools like HTML 5 Shims, and development practices like progressive enhancement, or graceful degergration should allow a web app to work even on most older clients provided they are used.

As for jQuery, unless you are specifically concerned about features exclusive to the 2.x codebase, you are still able to take advantage of the 1.x codebase, complete with updates (becuase they do still support it), which, via proressive enchancement, you could use a tool such as Modernizr to test for features specific to older IEs, and if true, load the lower codebase. 

http://blog.jquery.com/2014/01/24/jquery-1-11-and-2-1-released/

What I am basically saying here is, if you really wanted to, it's entirely possible to make the site work on older clients while still retaining everything for newer clients. As as a front end developer I really dislike having to support older editions of IE, but really, as long as Windows XP has a sizable marketshare supporting back to IE 8 isn't that hard or time consuming.

And yes, I agree if you are on Windows 7 or higher, you should be on IE 11 (chances are you were force upgraded to it with a Windows update and never noticed).