Error on my CentOS server

Using IPI No-Shortcut mode
XENBUS: Device with no driver: device/vbd/2049
XENBUS: Device with no driver: device/vif/0
md: Autodetecting RAID arrays.
md: autorun ...
md: ... autorun DONE.
VFS: Cannot open root device "sda1" or unknown-block(0,0)
Please append a correct "root=" boot option
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)

my config file is set to the following

kernel = "/boot/vmlinuz-2.6.18-128.1.16.el5xen"
memory = 256
name = "centos.5-4.x86"
vif = [ '' ]
disk = ['file:/var/stacklet/centos.5-4.x86.img,sda1,w']
root = "/dev/sda1"
extra = "fastboot"

my OS info

[root@backup2 xen]# cat /etc/redhat-release
CentOS release 5.2 (Final)
[root@backup2 xen]#

[root@backup2 xen]# rpm -qa | grep xen
kernel-xen-2.6.18-128.1.16.el5
xen-3.0.3-80.el5_3.3
xen-libs-3.0.3-80.el5_3.3

[root@backup2 xen]# uname -r
2.6.18-128.1.16.el5xen
[root@backup2 xen]#