The fastest way to replace GNOME's Metacity with XFWM4 in Ubuntu.

I replaced Metacity with XFWM because:
1. XFWM is faster. Xfce is much faster than GNOME, but I'm not using it because I have dial-up and I can't download such size(20+ MB). So I must replace window manager to make Ubuntu a little faster.
2. It supports built-in compositing. It can make menus, inactive windows, ... transparent without Compiz so I can use compositing on OpenGL-incompatible video card.
3. It has easy theming. XFWM uses XPM(X Pix Map) and PNG formats and a text file to create themes, unlike Metacity, that uses XML that I badly understand.
OK, let's start.
1. In Synaptic install package "xfwm4". Also, if you want to choose themes, install "xfce4-settings". Then if you want to run XFWM Settings, run: "xfce4-settings-manager &" in terminal.
2. Go to System->Settings->Startup Applications.
3. Click "+ Add".
4. In Command field, enter : "xfwm4 --replace".
5. Type something in Name field.
6. Click "+ Add".
7. Reboot and enjoy:).
As you will notice after reboot there will be a black screen for a short time. It's because autostart is not done immediately after log in. But it's the fastest way.