base.vdi images should be place into [installdir]/Drives directory on a speedLinux installation. Speedlinux uses coLinux kernel. If downloaded with the installer you don't have to do this yourself.
Link to Speedlinux Installer: https://sourceforge.net/projects/freetzlinux/
(This images may be used on coLinux without speedlinux installer as well, but then you have to know what you are doing. Out of the box functionality is only the case if used in combination with the speedlinux Installer. See posting on coLinux mailinglist : http://sourceforge.net/mailarchive/forum.php?thread_name=CA%2BUv17ykfJ52P03sw3dE-jiOnNzBuSZ-MU%2BEPamZX8Xo_sGpkA%40mail.gmail.com&forum_name=colinux-users)
The folder 'contributed' my be filled in future with images from other sources. All members of suorceforg.net may upload usable images. Please request the right to upload by sending a email with your account name to johann.pascher [at] gmail.com first.