... in a decade far, far away we used to use multi-user operating systems. Which used to keep one user's data private from another - unless they explicitly wished to share. They also let the sysadmin install software packages for everyone to use, or each user could run their own local programs - which could not access other user's data.

Sounds familiar? So why propose a "solution" that only gives application-layer (rather than OS-layer) protection between users? That only protects properly one (corporate) user - isn't my personal data of at least equal value? That can't easily be extended to several users (think "e-banking user" which shares no data at all with "games user")? And there's no inherent reason why the different user programs can't share the same display screen either, with different passwords and screen lock timeouts - so you don't need a password to run Angry Birds, but do to unlock your contacts.

+1 for this. Not at all geeky to use - it's a neat front end to partclone (partclone.org).
Compresses the filesystems, so it can be really fast to restore, especially if you clean it up (CCleaner) and defrag it first.
You can also put this on a bootable CD/DVD with the restore image.

Also consider how much time and money it takes *you* to install the systems in the first place. Especially if the PCs need to run an office suite, music, video and photo software.

What I've personally done is:
a) boot up Ubuntu off USB stick
b) wipe the whole hard drive using "dd if=/dev/zero of=/dev/sda bs=10M" (10 secs your time, 20-30 mins elapsed [typically ~2GB/minute])
c) Install Ubuntu (1 min your time, 10 mins elapsed when using USB)
d) Install updates (1 min your time, 30 mins elapsed if off internet, 10 mins if off USB).

If you are installing lots of machines, consider updating the USB with all updates. If you have older machines, consider Lubuntu instead. The OEM install is nice if you want the recipient to create the initial account.

If you need to use Windows, the same principles apply. Use a USB drive to install it, it's faster than CD. Download all pieces of software and updates, also to USB. But you will need to run rather more installers than with Ubuntu. How much is your time worth?

Quite right, installing pure Windows 7 on a newish machine is about as easy as installing Ubuntu.

Installing a usable computer system is another matter though. On Ubuntu, you already have office, music and photo software, and a few clicks on the Software Centre menus gets you any other software and codecs you want. On Windows, you will need to find quite a few more applications, each from their own website, and download and install them in a myriad of ways.

Wouldn't it be nice if there was a Windows App Store even half as good as any major distro's repository?

The logical conclusion should be we need to use complex passwords that don't need to be typed manually.
That tends to imply some hardware device (since pure software systems run the risk of compromise).
We've actually had these for some time - the crypto smartcards / phone SIM cards / etc that perform crypto challenge-response.
Some of these use public key crypto, so additionally there is no need to share your secret (i.e. private key) with anyone else.

We may sometimes need two-factor authentication, but the main reason is to ensure that the correct human is using the device, to the necessary level of assurance.

Note we also should not demand high authentication all the time - it tends to lead to social attacks / phishing. So for example it might be appropriate to only need the hardware device to allow access to see the balance of a bank account. (Which is much the same as just needing your cash card to enquire the balance over the counter.) But if you want to withdraw any sizeable sum, then demand a second factor (password/PIN) on each transaction.

I now offer people a Linux Live CD - such as Ubuntu. Tell them it will get their machine working, they can recover the files, and I won't need to see their private stuff.
Now if they are the type who like clicking "yes" to everything including the "install" option, well, that's another problem fixed for good.
Support by email - http://lmgtfy.com/ and http://giyf.com/ are good pointers.

What are they doing wrong?
Switching back to and end-of-life operating system (Windows XP). But why?

... since LEO, the first commercial business computer, was based on the EDSAC design. Amazingly LEO computers were still in use in 1981. Check out the LEO Computers Society.

Check out Seeed Studio scopes. They sell JYE Tech scope for $54, DSO Nano for $89. Fine if you don't need high sample rate, they are limited to 5M samples/sec or 1M samples/sec respectively.

But that Dell page does not tell the whole truth.

It advertises "Windows® . Life without WallsTM . Dell recommends Windows 7." but then goes on to have a screenshot of Windows XP.

And if you go to the Euro Dell site and try to look for Ubuntu systems
http://www1.euro.dell.com/content/topics/topic.aspx/emea/segments/gen/client/en/ubuntu_landing?c=uk&l=en&s=dhs
you find all the ones offered are only Windows 7.

So it advertises two operating systems (XP and Ubuntu) which it does not supply.