Pssst! Czae... Shoulda just played that off like you were messing with him... ;)
That's actually really funny. It's one of the "classics" of
computer stupidities (check out that site, it's good for hours of fun!). Basically, Windows holds on to some old and clunky DOS based methods for file naming. Even though pretty much every OS on the planet uses file headers to declare what kind of file something is (with extensions used, but only as a means of sorting files really), Windows actually uses it *first* due to backwards compatibility with DOS.
You can actually totally ***** up your computer pretty easily, since Windows now has a handy "open with" utility. If you right click a file, you'll often see an "open with" button. If you select it, you can map what utility to open that file with. There's also a handy "always use this" button, which essentially globally changes the associations within your Windows profile. So... if you for example remap your profile to always open .exe files with notepad (just an example, don't try this at home!), you'll basically break your system. If you don't have multiple user sessions defined on your box, the only way to fix it is to boot from a CD (although safe mode might work since that shouldn't load the profile).
It's pretty brain dead. The OS *should* look at the first X bytes of the file and see if there's a valid file header and use that utility first, then if it doesn't find one, fall back to the extension on the file (assume it's a file in a particular format, but written by an OS that doesn't put headers in). For some unfathomable reason Windows does it the other way around (actually just ignores file headers as far as I can tell).
The age old: "just change the extension" idea is hardly new... Still doesn't work, but it's not new. ;)