I followed this howto and the reason I signed up to your site is to work out why this is happening.
I have followed hundreds (spending around 8 hours yesterday trying to resolve this) of howtos.
This one I followed - http://www.howtoforge.com/centos_5.0_xen
gets me the furthest. I get through the text based centos install prompts and then start to install centos and when the installer wants to spin up the disk and get it ready to format it gives me the error:
"Input/output error during read on /dev/xvda" which from what I learnt means that the disk which centos is trying to install onto cannot be found/used/read/written.
I tried used "dd" to create a disk filled with zeros and that didnt work, tried formatting the drives (drive.img file) as ext3 and that didnt work cant for the life of me work out why and googling my ass off doesnt get me an answer either.
If you could shed some light, that would be wonderful!