Ubuntu reboot: kernel panic: VFS: unable to mount root fs on unknown block(0, 0)

[weiyun lv]

Ubuntu reboot: kernel panic-not syncing: VFS: unable to mount root fs on 
unknown block(0,0)

hello, I am a newbie and I met some problem which has puzzled me for a whole 
week:

1. install Ubuntu 5.04(I use ext2, for the second time ext3 as the file 
system), and gcc etc. no problem here.
2. download kernel source 2.6.10 from kernel.org
3. reconfig the kernel, only enable kernel-hacking options. (for the second 
time also ext3 file system)
4. make bzImage; make modules; make modules_install; make install. no error 
message given.
5. updata menu.lst and reboot. *****----> it gives above error message.
--------------------
5-1. I tried to use mkinitrd .... and added to the menu.lst too, but it 
doesn't work. And here I feel quiet unclear, some people say you need it, 
some say you don't need it and you should even delete it in menu.lst.

So, what can I do now, and the kernel-compiling is somewhat time-consuming.