Can I reset everything to its factory default settings?

I have got many problems on my dual-boot ubuntu 11.10. Unity interface always changes from 3D to 2D automatically, when I try to create login password it does not accept my root password, the look of folders always changes automatically,I'm always getting problems with repositories, update manager isn't working, software center doesn't find any internet connection while it actually exists , cannot minimize Google Chrome while I'm working with other applications, and so on.

I actually can't spend several hours on forums to fix that issues because I do not have much time for that. I want somewhat like easy way, by which you can store ALL settings (passwords, unity and so on) to its factory default settings.

Is there such a command or something like that to resolve this?

You can restore gnome-specific settings with the following commands in terminal:

rm -rf .gnome .gnome2 .gconf .gconfd .metacity

For details you can see How to Reset Ubuntu/Gnome Settings to Defaults without Re-installing | Linux FUD

Additionally you can verify that there are no broken dependencies using:

sudo apt-get check

And then you can troubleshoot your remaining problems one-by-one.

What I would suggest is to backup important files, insert the installation disc (or usb) then reinstall ubuntu. It will give you the option to wipe/install over the previous version. Then use nepomuk to make a backup after you've got everything installed.Make sure that you only backup things you need like your home folder and try to backup (i think) your ppa list