iBook g4 Dock is missing and drop down windows are empty

Recently I noticed that my hard drive was beginning to get full. So I did a search on finder for the largest files. I stumbled upon what looks like a 10gb backup dmg file. When i clicked on it in finder to see what was on it, my Ibook g4 suddenly switched fonts, my dock disappeared and I can't even minimize windows. When I highlight a drop down window for Finder or Edit or anything else on the desktop they just look blank with no selections available. I see that all of my files are here and I can click on a number of things, including disk utility. I repaired my hard drive using the disk utility and I still can't see my dock. Nothings changed. I feel like the dmg file hijacked my desktop but I can't figure out how to get back to my old desktop. Help please.

Welcome to the Forum. My guess is you are likely to be on Tiger, so download and install this.

I have 10.4.7. Have you heard of the dmg taking over your OS and even after restarting it wont enable the dock and the drop downs are blank when mouse over them? Is there just a simple return to the old desktop that clicking on the dmg backup file engaged?

So using that Combo updater should sort things for you.

I installed the PPC combo update and the drop downs are still blank and the dock still wont pop up

I have heard of strange events when the drive gets too full. If you have a current back up it may well be worth doing an erase and install of new OS - followed by combo update in turn followed by running software update from Apple menu. Once you have that set up well worth adding another Admin User for future troubleshooting etc.
Then drag files across from back up as you need them.