xen + redhat

I was working on XEN and had redhat running on it.

 I had created a file which I mounted and used as a disk image. Now I
thought that I was modifying the /etc/fstab on this mounted file, but
instead I modified the actual(on the root filesystem) /etc/fstab.

 Now on booting linux tells me 

Checking root filesystem 
Possibly non-existent or swap device? 
fsck.ext2: No such device or address while trying to open /dev/sda1 

This is true because /dev/sda1 is a mounted filesytem and not a real harddisk.

I removed the entry which pointed the root filesystem to be on
/dev/hda1. I tried using a boot floppy but no use it simply loads the
kernel from the floppy and then continues to load the disk image by
reading /etc/fstab.


all i want is to get a shell where i can modify /etc/fstab.


thanks.
deepak