unable to add/remove applications..

Thank you for taking the time to report this issue and helping to make Ubuntu better. Examining the information you have given us, this does not appear to be a bug report so we are closing it and converting it to a question in the support tracker. We appreciate the difficulties you are facing, but it would make more sense to raise problems you are having in the support tracker at https://answers.launchpad.net/ubuntu if you are uncertain if they are bugs. For help on reporting bugs, see https://help.ubuntu.com/community/ReportingBugs .

Yes, you need extra privileges to run that command. Try to execute "sudo dpkg --configure -a" instead. You will be prompted for your password, enter it and press return (even if you don't see any response on the screen while typing).

thank you for all that. I just typed that into the terminal, and entered my password. It didnt say anything after that(I'm not sure that it was supposed to?) but now I see my package manager is working. Will this fix the problem the computer was facing, and now allow me to add/remove programs again? Thanks for your help.. I am very frustrated with this computer, as you can probably understand! thank you!!

You are right, the command doesn't say much if it doesn't run into problems. If the package manager starts without errors or warnings it should be possible to remove applications again.

Okay.. now I went into add/remove.. and now it just runs.. I click on something to "un-check" it to remove, and it just runs and runs the "hourglass".. it will not let me check or un-check any programs.
I thank you for your help! you are very kind.

If it's still running endlessly you can kill the process via
system administration -> system monitor -> process tab

I'd suggest, since you run out of space and GUIs are freezing, you may remove apps via terminal using apt-get.
https://help.ubuntu.com/community/AptGet/Howto#Removal%20commands

e.g. to clean up package management with one line:
sudo apt-get autoremove && sudo apt-get clean && sudo apt-get autoclean

Unless you don't clean up the system it refuses to run intensive processed apps.

Interesting at the moment is to find out if your trash is full, (the trash applet should be on your panel), if not, open Nautilus menu -> go to -> trash.
Take also a look into system administration -> computer janitor

Another option is to boot into recovery mode, there should be an option to clear space.

You strictly need to open a Terminal from the menu Applications->Accessories->Terminal and type:

sudo dpkg --configure -a

give your user password when requested, you don't see nothing when you type it, then press enter.
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But to fully check and upgrade your system using terminal using command line,
open a Terminal from the menu Applications->Accessories->Terminal

Tip: right click with mouse on the terminal title caption and select the item "Always on Top" doing this you will force the terminal window to stay on top of the other windows and you will find very easy to copy single row from this web page into the terminal...
Something more about using the terminal https://help.ubuntu.com/community/UsingTheTerminal

Then type or better copy and paste a row a time then press enter:
(Tip: select the single row to copy then right click into the terminal and to quick paste click with middle button of mouse )

sudo dpkg --configure -a
sudo apt-get -f install
sudo apt-get --fix-missing install
sudo apt-get clean
sudo apt-get update
sudo apt-get dist-upgrade
sudo apt-get clean
sudo apt-get autoremove

give your user password when requested, you don't see nothing when you type it, then press enter.

Hope this helps