MBA mid 2011 with Bootcamp Win7-HP: changed text size, now desktop Black, but will display Taskmgr

As title says, I have bootcamp installed on MBA (mid 2011) using Win7 HP. Both OS were working fine until I tried to increase the text size on the Win side by doing a Rt-Click on the desktop. Now the screen is black with only the mouse showing. If I use one of several keyboard shortcuts, the expected window is displayed properly, eg Taskmgr or Command-p to display the projector option. One keyboard combination (I've tried many) brought up a Chrome browser window and it behaves normally and appears to have a normal resolution. But the taskbar is not present nor is there a Start button, etc. When I minimize the browser, the screen goes black as before.

What can I do to get the normal Win7 desktop to display?