As the message says, the VirtualBox Linux kernel driver for the running Linux kernel isn't installed.
To re-setup the kernel module you just need to:
$ sudo /etc/init.d/vboxdrv setup
$ sudo /etc/init.d/vboxdrv setup
$ sudo vol_id -u /dev/sdb1
$ sudo mkdir /media/storage
$ sudo gedit /etc/fstab
UUID=ad02cb4e-f9cf-491a-b661-d96ed2c456be /media/storage ext3 relatime 0 2
$ sudo chown -R youruser:youruser /media/storage
$ sudo chmod -R 755 /media/storage
$ sudo apt-get install tree
$ tree /dev/disk
$ sudo ls -l /dev/disk/by-label
/home/youruser/Dropbox/folderA/
/home/youruser/Dropbox/fileA.txt
C:\My Dropbox\folderA\In this examples, the folder folderA and every file and folder inside, and the file fileA.txt, are synced between both computers.
C:\My Dropbox\fileA.txt
$ ln -s '/storage/outsidefolder/fileB.txt' '/home/youruser/Dropbox/insidefolder'The fileB.txt and the folderB will be synced into your "Dropbox folder" and synced into the the "Dropbox folder" in Computer B.
$ ln -s '/storage/outsidefolder/folderB' '/home/youruser/Dropbox/insidefolder'
$ gconftool -s --type bool /apps/update-notifier/auto_launch false
$ killall update-notifier
$ update-notifier &
$ disown
$ gconftool -s --type bool /apps/update-notifier/auto_launch true
deb http://ppa.launchpad.net/do-core/ppa/ubuntu jaunty mainInstall GNOME Do
deb-src http://ppa.launchpad.net/do-core/ppa/ubuntu jaunty main
$ sudo apt-get install gnome-doIt's that easy.