Kernel panic : VFS : unable to mount root fs on 03:02 error

hi there i'm very new to compiling a new kernel and i'm facing with an error which says

Code:

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Kernel panic : VFS : unable to mount root fs on 03:02

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on the other hand, i installed Red Hat via Virtual Box on windows 7. and you can see the steps i followed to compile my new kernel

$ make mrproper
$ make menuconfig

Code:

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$ make dep
$ make clean
$ make bzImage
$ ls -l arch/i386/boot (to check if Image was created or not)
$ make modules
$ make modules_install
$ /sbin/mkinitrd /boot/initrd-2.4.20-100.img 2.4.20-100
$ cp arch/i386/boot/bzImage /boot/bzImage-KERNEL_VERSION
$ cp System.map /boot/System.map-KERNEL_VERSION
$ ln -s /boot/System.map-KERNEL_VERSION /boot/System.map

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and after i compiled new kernel i editted /etc/grub.conf with adding lines

title My Opsys Kernel (2.4.20-100)
root (hd0,0)
kernel /bzImage-2.4.20-100 ro root=/dev/hda2 hdc=ide-scsi
initrd /initrd-2.4.20-100.img

What matters is how you configured the kernel before making it. If you're not using an initrd, you need to have three things compiled right in, not as modules: your hard drive motherboard controller, your hard drive driver (probably PATA/SATA in a modern kernel) and your root filesystem driver (for example ext3). If you are using an initrd, you need to create one (most distros have a script for that called something like mkinitrd).

Building a kernel is tricky if you don't know what you are doing. Do you have a special reason for wanting to build one?