After installing base, check your sources.list
It should have something like:
Code:
# Stable
deb http://http.us.debian.org/debian/ squeeze main contrib non-free
# Stable Sources
deb-src http://http.us.debian.org/debian/ squeeze main contrib non-free
# Security Updates http://www.debian.org/security/
deb http://security.debian.org/ squeeze/updates main contrib non-free
# Squeeze-updates
deb http://http.us.debian.org/debian/ squeeze-updates main contrib non-free
If not edit it.
apt-get update
apt-get install lxde xorg