Error " kernel panic -not syncing " after compiling new kernel

[Rocafort8]

Yesterday i tryed to do my first kernel compilation, and when i try to load it i get the error:

[ 0.624435] Kernel panic - not syncing: VFS : Unable to mount root fs on unknown-block (0,0)

The steps i followed are the next:

1-Download the kernel and place it in /usr/src/linux-headers-2.6.31/
2-make menuconfig and load the old configuration
3-Make
4-make modules
5-make modules_install
6-make install

So i go to the /boot/ folder and i found the new files System.map-2.6.31, vmlinuz-2.6.31 and config-2.6.31.

I noticed that the other kernel i have already installed ( 2.6.24 ) have an initrd.img-2.6.24-generic file, i tryed yaird to generate it, but it throws me the following errors:

mkinitrd.yaird -o/boot/initrd.img-2.6.31-generic 2.6.31

yaird error: unrecognised device: /sys/devices/platform/i8042/serio0/input
yaird error: unrecognised device: /sys/devices/platform/i8042/serio0/input/input1
yaird error: unrecognised device: /sys/devices/virtual
yaird error: unrecognised device: /sys/devices/virtual/input
yaird error: unrecognised device: /sys/devices/virtual/input/input5
yaird error: unrecognised device: /sys/devices/virtual
yaird error: unrecognised device: /sys/devices/virtual/input
yaird error: unrecognised device: /sys/devices/virtual/input/input6
yaird error: unrecognised device: /sys/devices/LNXSYSTM:00
yaird error: unrecognised device: /sys/devices/LNXSYSTM:00/device:00
yaird error: unrecognised device: /sys/devices/LNXSYSTM:00/device:00/PNP0A03:00
yaird error: unrecognised device: /sys/devices/LNXSYSTM:00/device:00/PNP0A03:00/LNXVIDEO:00
yaird error: unrecognised device: /sys/devices/LNXSYSTM:00/device:00/PNP0A03:00/LNXVIDEO:00/input
yaird error: unrecognised device: /sys/devices/LNXSYSTM:00/device:00/PNP0A03:00/LNXVIDEO:00/input/input7
yaird error: unrecognised device: /sys/devices/LNXSYSTM:00
yaird error: unrecognised device: /sys/devices/LNXSYSTM:00/device:00
yaird error: unrecognised device: /sys/devices/LNXSYSTM:00/device:00/PNP0A03:00
yaird error: unrecognised device: /sys/devices/LNXSYSTM:00/device:00/PNP0A03:00/LNXVIDEO:01
yaird error: unrecognised device: /sys/devices/LNXSYSTM:00/device:00/PNP0A03:00/LNXVIDEO:01/input
yaird error: unrecognised device: /sys/devices/LNXSYSTM:00/device:00/PNP0A03:00/LNXVIDEO:01/input/input8
yaird error: unrecognised device: /sys/devices/virtual
yaird error: unrecognised device: /sys/devices/virtual/input
yaird error: unrecognised device: /sys/devices/virtual/input/input9
yaird error: uuid '1e70b5e1-2e16-48d3-a99f-c01c1d6d2e2e' not found (/etc/fstab:6) (fatal).