Hey practical
Truthfully, I would dual boot RHEL6, or better yet, put it on a seperate hdd and dual boot that OS.
As for the VM, did you try contacting RH and ask them what the initrd file parameters should be. And also what kind of VM footprint it would take?? 3 Gigs seems a little bit low. I would say that you need 8 gigs or better to VM it with full functionality..... really.
I have run into issues with VM's trying to run full sized distros and the mem allocation size doesn't cut it. [ meaning that the OS takes up too much space]. So my SuSe and Ubuntu spins run on their own PC's.
Now maybe you don't have another PC kicking around to put RHEL6 on , but you might have a another Hdd, 100 gigs in size, or better 160 gigs is good.
I know the argument here is that it makes it a hassle switching back to windows on the fly, but really , consider it.
CAVEAT .. pay attention to the following text....
Putting Linux [ any Distro ] on the same hdd as windows is a major "no no". This is because the GRUB will offset the windows MBR, and removal of linux not using grub will not reset the windows MBR to its proper spot , and then windows AND linux are gone for toast, hence my suggesting that linux go on its own drive. Or better... Its own PC.
for most PC's at boot pressing F10, at POST, will invoke the BOOT select menu , [a work around if grub hates your set up on your distro install to "other" hdd],then you can select either your windows or linux drive at POST on boot.
So Contact RH, that spin of yours allows phone call assistance on the required mem for a VM boot
Hope this helps
L-R