RHEL4 working ok ...
I noticed this post now ... I know it's been awhile, but since no one has updated, I guess I can add a comment. I just tested out installing RHEL4u4. Note that 64bit is not supported on the OS X versions yet ... keep sending them e-mails requesting this so they can get this software up to par. So if you use the 32bit version, it installs fine. I run it with 512 MB of RAM and it works fine. Note there's no parallels tools for RHEL period. They're working on that too ...
so you'll see some problems with X-windows. On this Macbook Pro, I can only run 1280 resolution so parts of the screen is not being used. I also noticed it has major problems resetting X. Ctrl-Alt-Delete is a commonly known X restart key combination, it fails and craps out. You have to forcefully kill the VM and start over. I am running the kernel with apm=off since I don't trust the power management. I can see how maybe you could run with noapci. Play around with kernel options and see if you can find the best fit. Other things are turning off services you don't need. Tons of those in RHEL to make it boot faster. So in short, yes it works, but so far I haven't found a fix to get full screen to fill out the whole screen.
Later