You can donwload directly the latest installer for Windows at odoo_8.0-latest.exe any time & install/reinstall it. This link always points to latest version at nightly repository of openerp, practically it's updated almost every day.

UPDATE:
in Debian/Ubuntu you can install/update using apt-get as it explained at: http://nightly.odoo.com/

in Ubuntu you've to run commands:

- for installation

1) sudo echo 'deb http://nightly.odoo.com/8.0/nightly/deb/ ./ '  > /etc/apt/sources.list.d/odoo8.list

2) sudo apt-get update

3) sudo apt-get install odoo

- for update:

1) sudo apt-get update

2) sudo apt-get upgrade

- for start/stop/restart/status:

 sudo service odoo <here start or stop or restart or status >

Go to https://www.odoo.com/page/download

& Fill the form then download and Install , Setup includes all stuff Python,PostGRES means everything included in package. Simple Download and Run the exe file and follow the simple steps.