Now that Ubuntu Maverick Meerkat 10.04 has gone out of support you will need to upgrade your distro to continue receiving security updates.
Unfortunately (in my opinion), Ubuntu has switched their default desktop from Gnome to a new user interface called Unity which is not an evolutionary step but a completely new user interface which will be very foreign to some users and will require a new learning curve to get up to speed with it.
Personally, I don't have time for this and I don't appreciate a new paradigm being forced upon me which disrupts my productivity so I want my old (Classic) desktop back. Here is how:
On the login screen, click your username.

Now look at the bottom of the screen and you will see 3 combo boxes.

Open the 3rd combo box (the one on the right) and you will be able to select Ubuntu Classic desktop.
I have heard this option will disappear in later Ubuntu versions and at that point I will probably change distro to Debian or perhaps Mint.