when starting linux "cannot open root device"
 

I'm using Lilo 22.5.9 boot loader to load slackware.
while linux is loading it freezes and the last lines of text say

VFS: cannot open root device "301" or 03:01
Please append a correct "root=" boot option
kernel panic: unable to mount root fs on 03:01

I'm new with linux, this is my first time installing it and I had it working before, but now when I go to load it up this error message always pops up and the computer freezes. Does anyone know what I should do?

Check out 2.3 How Can I Interact at Boot Time?
http://www.tldp.org/HOWTO/LILO-2.html#ss2.3

You must have support for the root filesystem (ie ext3, reiserfs) compiled into the kernel. If you do not, you must use init ram disk (initrd).

To find out which filesystems are compiled as what, look for your kernel config file in /boot and search for FS. Like this for my setup:
To make a initrd look at the link listed above.