InformatiQ

i only tested thes instructions on Ubuntu, but it should work with any distro for the sake of this post we will call a running linux distro "pmachine" and a xen guest "vmachine" 

1. you need t otake a copy of the installation of the pmachine, this could be done in two ways
2. create vmachine "data disk" as explained in xen-vmachine-howto
3. copy all files from the pmachine backup to the new data disk
4. remove the /boot directory of the vmachine data disk
5. copy /lib of the pmachine to /lib of the vmachine
6. create the xen guest config file
7. and you should be done

this will create a vmachine based on the pmachine but with a different kernel (a generic kernel provided by your xen host)if you want to have the same kernel of the pmachine, then you will have to

1. install a xen kernel into the pmachine
2. copy over all contens of the /boot of the pmachine to /boot of the xen host
3. use the kernel image copied over from the pmachine as the kernel of the vmachine in the xen guest config file
4. do not copy /lib to the vmachine