Disable file preview in VS2012

In VS2012 when you select a file in solution explorer it automatically opens file in a special "preview" tab.

Maybe my computer is not fast enough, but this preview is too slow for my taste.

How do I disable this feature?

In Tools > Options > Environment > Tabs and Windows, you can disable it by unckecking "Solution explorer" under Preview tab.

I find it using the "Quick launch" new feature. Simply type "preview", and a link to the setting will be suggested. Great new feature of VS

You can also toggle file preview within the Solution Explorer tool-window itself:

This may have been added in the July update because I hadn't noticed it before then.

One of the buttons at the top of the solution explorer toggles whether this is enabled.