i really want to try it out but it just refused to install on virtualbox. i allocated 128mb ram, ide 8g hdd, 16mb vram, pcnet fast II, piix chiset to it.
my processor is core i7 720q. i heard that it wont run on pentium 4 or newer processors, is there any work around?

If you have an ISO i can possibly make you a VHD of it... Ive used this before and had it working in Virtual Machine, not virtual box. Let me try if you have the ISO.

Link is already provided here. I'm currently trying it on VMware Workstation, and bootup is stuck at here (installation is finished).

Disable the Network Card (or better remove it completely from the VM options)?

Then I can login, with no network available. Is there any idea about making it work?
Nevertheless I can run the OS in VMware anyways.

How long did you wait for it? It's just trying to resolve network settings at this stage, and may eventually time out by itself after a few minutes.

If it doesn't, the first thing you need to do is get the OS up and running, either by 1) disabling the network card in VMware settings or 2) by booting redhat into single user mode (when the bootloader (grub?) first appears, push whatever key you need to edit the boot line, and change the kernel line by adding the word "single" (lowercase, no quotes) to the end.)

Once the system is up, I would suggest the following: edit the file /etc/sysconfig/network-scripts/ifcfg-eth0. The ONBOOT parameter may or may not be defined, but either way, set ONBOOT=no, then save the file and reboot.

This will at least allow you to successfully boot the OS with the NIC enabled. You'll still need to configure it to get internet access, but maybe you can do that from the GUI. It may be that DHCP configuration won't work in that old version of linux, and if that's the case, then you'll need to manually set your IP address and subnet mask appropriately.

Jeffbai, any technical information about your problem?

I'm still running 6.2 in virtualbox / networked, never tried 6.1

I have 4.2 networked in VMWare

Nice one!
Do you think redhat 4.0 (colgate) can be run ?

roytam, do you have an ISO for 4.2?

No I don't have ISO image. I used boot floppy and setup a ftp server for netinstall.

I think so.
Even Debian 0.93R6 works with networking in VMWare.