I know little about Linux and have only succesfulyy started it about 5 times. Spontaneously, Linux does not start, but says
INIT: No inittab file found
Enter runlevel:

I tried entering numbers... (for a level, right?) but nothing does anything. If I don't enter a number, it only repeats the prompt. if I do, it says

INIT: entering runlevel (whatever)
INIT: no more prcesses left to run in this runlevel
And then I can do nothing else but turn off the power. I have no idea what to do.

Do you have created a bootdisk during the installation?

If so, use it to boot and mount the root partition:

mount -t ext2 /dev/hdxy /mnt

Where x is the position of your hd
(a=ide1-master,b=ide1-slave,c=ide2-master,d=ide2-slave)
and y is the number of the root partition

Check if you have the inittab file in your hard disk, if you mount
the root partition in /mnt you should look for:

/mnt/etc/inittab

If you dont have it copy it (from a friend?)
or tell us what distro do you have and probably someone will post the inittab

Also check if you have a directory:

/mnt/etc/rc.d

And something inside it

Hope this is correct . . . . . . ^_^