Mini adapter to HDMI cable into my tv. No problem streaming movies last night, today all I see is some default apple background on my tv. Don't know quite what to do in System Pref's and Appearances. Please Help

Question

I know its an issue with the computer because when I messed with Appearance settings in System Preferences, the tv picture changed.
thanks
CB

Answer 1

How were you "streaming movies last night"?  (What application?)
It may also be useful to know your specific iMac model, and the version of Mac OS X it runs.  This list may help identify your iMac model.
http://www.everymac.com/systems/apple/imac/index-imac.html
So, this is an iMac, and you have an HDTV attached to it as its second screen...  Is that correct?
Typically, if the HDTV is acting as the iMac's second screen, it is extending the Desktop.  I'm thinking that when you had "no problem" last night, it was set so that the second screen was mirroring what was on the iMac's screen (NOT extending the Desktop).  In other words, if you had the movie playing at full screen on the iMac's screen, the same thing appeared on the HDTV screen.
You may have changed that setting so that it is not mirroring anymore.  The second screen would then be extending the Desktop.  In that case, you would see the "default Apple background" on it until you moved something onto that part of the Desktop (like an open window).
Open System Preferences Displays pane.  Go to the Arrangement tab.  If the diagram there shows representations of two screen (the iMac's screen and the HDTV screen), the HDTV is set to extend the Desktop.  The setting (checkbox) for mirroring should be there, toward the bottom.
However, mirroring is probably NOT the best setting for your setup.  If what I wrote so far has been relevant for your original question, you can post back for additional info...