There are a handful of situations where securely erasing data can be useful. If you're about to sell-on a computer, or even if you're about to dispose of it, it makes sense to completely wipe the hard disk.
Have you got a vintage camera that won't work under Ubuntu because it's not a removable storage device (which is to say, its contents don't appear in a file browsing window when you attach the camera)?
Sometimes if a USB memory stick or memory card stops working correctly, the best plan is to reformat it. To do this under Ubuntu, follow the steps below. Note that the instructions are extremely thorough - first the partition on the memory stick is deleted, then a new one is
created and subsequently formatted.
If you don't fancy carrying the delicate Ubuntu installation CD around with you, you can copy its contents to a USB key stick and use that to install Ubuntu onto computers (provided those computers can boot from USB, and most modern computers will be able to).
If you opt to share folders across a network under Ubuntu you'll find they're protected with your username and password, which you might not want to share with others. The Shared Folders dialog box allows you to setup guest access but, at the time of writing, this had a serious
bug that rendered it unusable.
To begin a Remote Assistance session, the novice must ask for help. That's done through either an instant messaging program or by opening the Remote Assistance program and sending an invitation file.
You can optimize Vista all you want, possibly shaving 15 or 20 seconds off your boot time, or you can approach the problem from a different angle.