I have recently followed the following guides:
After POST, GRUB loads but does nothing.
When I try to specify the kernel by hand with: "kernel /boot/vmlinuz root=/dev/sda5" (however I also tried different root options, like /dev/mapper/root and sda7) I get "Error 15: File not found"
sda1, sda2, sda3 are Windows/recovery partitions, sda4 is extended, sda5 is my root, sda6 is swap and sda7 is my root.
My /boot/grub/grub.conf is:
kernel /boot/vmlinuz root=/dev/mapper/root