make sure kernel compilation tools are installed
make sure your on the sudoers list
mkdir Xen
cd Xen
wget http://www.cl.cam.ac.uk/Research/SRG/netos/xen/downloads/xen-unstable.hg.tar.gz
tar zxvf xen-unstable.hg.tar.gz
cd xen-unstable.hg
hg pull -u
hg identify---> returns c5286130a96e tip or other (use this hash it works set for this hash)
cd  ..
cd ..
wget ftp://ftp.kernel.org/pub/linux/kernel/v2.6/testing/linux-2.6.16-rc5.tar.gz
tar zxvf linux-2.6.16-rc5.tar.gz
cd Xen
cd xen-unstable
#####mkbuildtree ~/linux-2.6.16-rc5
cd ~/xen/xen-unstable.hg/linux-2.6-xen-sparse/
./mkbuildtree ~/xen/linux-2.6.16-rc5
cd linux-2.6.16-rc5.tar.gz
sudo make menuconfig CC=gcc-3.3 HOSTCC=gcc-3.3
sudo make CC=gcc-3.3 HOSTCC=gcc-3.3
sudo make install CC=gcc-4.4 HOSTCC=gcc-3.3
sudo make modules CC=gcc-3.3 HOSTCC=gcc-3.3
sudo make modules_install CC=gcc-3.3 HOSTCC=gcc-3.3
sudo make install install-xen CC=gcc-3.3 HOSTCC=gcc-3.3 
sudo make install-tools CC=gcc-3.3 HOSTCC=gcc-3.3
hikenboot zaid the command to revert to a particular hash is "tag <hash number>
hikenboot hold on looking for the mercurial tools
hikenboot Mercurial is available at:
hikenboot   http://www.selenic.com/mercurial/ 
hikenboot You will also need a Python version >= 2.3