No error messages. Installation did complete without error messages and I have never had Lightroom on this computer. The Lr logo appears on my homepage and when access it, there is a momentary flash of the spinning blue symbol suggesting it is accessing. The Lr logo then appears in the tool bar at the bottom of my screen with other "open" programs. If I move the cursor over it, the image of a Lr screen appears (too small to read) but cannot be accessed.
It sounds like LR is running with its window off the screen. Do you have a multimonitor system with one or more of the monitors turned off?
Try this: put your cursor on the too-small-to-read little window you mentioned, right-click to get a context menu, and click on "Move". Then without moving the mouse first, click and hold the left button down and drag the mouse around until it's on your screen. Did it drag the LR window with it?