it's completely unnecessary to run a virtual machine or a chroot just for skype.
if you download the statically linked (not requiring system dependancies) skype distributable, you can run both Skype 4.0 and Skype 2.2 on the same system.
install skype 4.0 using the deb, and download the statically linked version of skype 2.2 and extract it to
/opt and then add
/opt/skype-VERSION to your
skype executable in
/opt/skype-VERSION to something like
and once you've done all of that, you should be able to run
skype for either version.
here's Skype 2.2 static: http://download.skype.com/linux/skype_static-220.127.116.11.tar.bz2