why did my desktop background change?

neither Hacked, bug nor Updated, but the picture you used for Background as changed location.

This happened to me too. I didn't know why until I remembered that I had earlier saved that photo to an external hard drive and deleted it from my computer. So, the computer automatically removed it from the desktop and replaced it with a generic Apple one. Hope this helps!

Earlier versions of Tiger OS X 10.4.x were less stable than the last

Combo update step OS X 10.4.11; so that was advised to update that

and any other applications that would be seen as needing an update

after that, as Software Update can still find vintage update bits to

other iLife, etc parts (if lucky) and one could try & find vintage Flash

from the Adobe archive, too.

With Tiger and older OS X versions, to start up on SafeBoot mode

then run Disk Utility's 'repair disk permissions' may help some of

the odd behavior sometimes encountered without known cause.

Per the final update step to OS X 10.4.11, using the Combo update;

this is often much more stable and successful, if one makes a backup

of the applications and other user account items, then perform an

all-new system installation on a wiped hard drive (reformat, etc) and

use the last version combo and final updates for all available items.

This can often result in former issues not reappearing in Tiger 10.4.11.

And odd ones less common, never appearing; final Combo is best.

So, if you are already running the 10.4.11, get and reinstall the Combo

version 10.4.11 over the top of your current Tiger system. And repair

disk permissions again. - Also, if the original hard drive is still working,

it may be time to consider replacement, since corruption or failure may

be part of odd behaviors outside of file damage or overwriting.

Good luck & happy computing! 🙂

Open the Desktop & Screen Saver pane of System Preferences and check if it's set to change the picture.

(111428)

Is the Dock the same as always?

In System Preferences>Accounts, how many show there?

If you change it to what it was, does it survive a restart?