single-user mode can't boot
 

c:win98se d:redhat9.0 installed on one hard drive.
grub boot loader installed.
root password foreget, so linux single-user mode would go.

grub version
redhat linux(2.4.20-8) -->selected
dos

'e'key typed, follwoing edit screen appear
root(hd0, 1)
kernel /vmlinuz-2.4.20-8 ro root=label=/ -->selected
initrd /initrd-2.4.20-8.img

'e' key typed,follwoing edit screen appear
grub edit> kernel /vmlinuz-2.4.20-8 ro root=label=/

move a cursor to end line, single typed
grub edit> kernel /vmlinuz-2.4.20-8 ro root=label=/ single

'b'key typed. booting processed.
below letter appear in end line. cursor blink, booting stopped..
sh-2.05b#

what's problem?

There is no problem with that.
The prompt indicates you have booted in single-user mode.

Thanks