RHEL in Virtual Box; host system file access

RHEL 5.8 is up in a Virtual Box VM, but I can't do much evaluating without access to my host machine's files. I need Shared Folders, ergo I need Guest Additions. However I get [FAILED] for "Building the main Guest Additions module". It refers me to a logfile and there I see: [Dang, sure wish I had Guest Additions so I could do birectional clipboard access :-(]

/tmp/vbox.0/Makefile.include.header:97: *** Error: unable to
find the sources of your current Linux kernel. Specify
KERN_DIR= and run Make again.  Stop.

There is stuff on the net about this, e.g. http://www.if-not-true-then-false.com/2010/install-virtualbox-guest-additions-on-fedora-centos-red-hat-rhel/ but besides leaving me confused it also didn't work. First I ran into the yum command saying: `Unable to read consumer identity` -->  https://access.redhat.com/knowledge/solutions/78153  More confusion and the steps didn't help.

Truth is I don't want my server system sullied by development tools. I don't really want to 'yum install gcc' (even if I could). I want to be free of accidental dependencies. So maybe Guest Additions isn't the way to go. Is there another way to get access to my host system's files?

Thanks, /Andy.