I mistakenly deleted my drop down menu,with all my programs etc,I

I assume you mean the menu that says:
"Applications Places System"

Installing 10.10 should restore that, yes, but you can actually get it back without installing anything. Right-click the panel and choose "Add to Panel...". Then add the "Menu Bar" applet. Drag it into place if necessary, then right-click it and choose "Lock to Panel".

Please try this to restore standard desktop...

How to restore gnome panels and toolbars disappered on Ubuntu

A) When you see the clean desktop without toolbar:
- press ALT+F2 a little window will come in front of you
- ins this window field type:

gnome-terminal

Then press enter a terminal window will come in front of you:

type (a single row a time then press enter) :

gconftool --recursive-unset /apps/panel;
rm -rf $HOME/.gconf/apps/panel;
pkill gnome-panel

B) if you cannot get access to terminal using method A then:
- press ctrl + alt + F2 you will get a pseudo terminal black screen in front of you
- Make login with your user and password (when you type the password you will not see any screen chars, so type in then press enter)
- then when you get access, type (a single row a time then press enter) :

gconftool --recursive-unset /apps/panel;
rm -rf $HOME/.gconf/apps/panel;
pkill gnome-panel

Then press ctrl + alt + F7 to return to your desktop

Hope this helps