Our house had a tiny little nook that didn't quite have a purpose. It was at one time our son's room, a place for an armoire, we thought it could be an extra bedroom, but we finally decided to make it into a small office.
After searching for the perfect office/computer desk with lots of paper storage, etc., and not finding anything to fit in such a small space, we decided that we had better build it ourselves. So I perused Craigslist and found a wooden filing cabinet.
It had a beautiful light wood color and brass handles and label holders. Nice, but just not me. So, I used Glisser Sander Deglosser and some leftover white paint for the cabinet itself and oil-rubbed bronze spray paint for the brass fixings.
We placed the filing drawer against the wall (that was part of our built-in-partially see-through bookcase (to utilize the big window that had previously been hiding behind the wall in our basement stairwell)). Then added a little shelf for the CPU and made a very skinny top for the printer, monitor, speakers and any other items that the top of a computer desk holds.
To build the desk:
Then I caulked, sanded some more, and primed the piece.
In the picture below, the keyboard is on top of the desk. However, my father had a pull-out keyboard tray that he wasn't using anymore. It was black...so, of course, I spray painted it white. Screwed it into the bottom of the desk and it worked perfectly!