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 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-3.3 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
cd ~/xen/2/xen-unstable.hg
sudo make install-xen CC=gcc-3.3 HOSTCC=gcc-3.3 
sudo make install-tools CC=gcc-3.3 HOSTCC=gcc-3.3
cd /lib/modules
ls
sudo depmod 2.6.16-rc6

sudo /usr/sbin/mkinitrd -o /boot/xen-2.6.16-rc6.img 2.6.16-rc6

 tar zxvf /tmp/download/hdparm-3.6.tar.gz
 cd hdparm-3.5
 make
 su root
 (type password when prompted)
 make install
 cp /usr/local/sbin/hdparm /sbin/hdparm
 exit

To enable DMA for a hard drive: hdparm -d1 /dev/hda

To disable DMA for a hard drive: hdparm -d0 /dev/hda

To measure transfer rate of a hard drive: hdparm -Tt /dev/hda

To see what options are enabled for a hard drive: hdparm /dev/hda 
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