debian lenny (or ubuntu lucid for that matter) does not ship with python2.7, so you have to install it from its source. Run everything as root.
aptitude install libsqlite3-dev zlib1g-dev libssl-dev libbz2-dev libncurses5-dev libreadline6-dev #for tkinter support also install tcl-dev libgdbm-dev cd /opt wget -O- http://python.org/ftp/python/2.7.2/Python-2.7.2.tgz | tar xz cd Python-2.7.2 ./configure --with-threads --enable-shared --prefix=/opt/python2.7 make make altinstall ln -s /opt/python2.7/lib/libpython2.7.so.1.0 /usr/lib64/ ln -s /opt/python2.7/lib/libpython2.7.so /usr/ cd /opt/python2.7 wget http://peak.telecommunity.com/dist/ez_setup.py /opt/python2.7/bin/python2.7 ez_setup.py wget -O- http://pypi.python.org/packages/source/p/pip/pip-1.0.tar.gz | tar xz cd pip-1.0 /opt/python2.7/bin/python2.7 setup.py install /opt/python2.7/bin/pip install virtualenv