Not only the U.K.,
Windows 7 is already on sale in Israel.

For me on the same machine 3.5 is much faster.

It's possible it might be taking more ram and on your old hardware with less ram it's using swapped memory, which is very very slow.

I haven't run an active Anti-Virus software once in all my years of computing (over 20) and the only virus I have ever contracted on Windows was the Blaster worm that relied on a publicly unknown (at the time) bug in one of Microsoft's DLL.

How did I do this for so long? Awareness, Patching and Prudence.

On the other hand, I know plenty of people running active commercial anti-virus software that's been plagued with virii.

The reason?
1. No Awareness.
2. No Patching.
3. No Prudence.

Worm/Virus are spread so fast these days, the AV software just can't catch up in time to prevent the infection and in quite a few cases, the Worm/Virus disables the AV software, making it more difficult (in some cases impossible) to remove the infection without booting to another OS (Live OS from a CD/USB Drive).

That's why I use ClamWin for occasional scanning.

I call BS.

When dealing with 3D content, you'll have new encoding techniques (since the 2D images are not too dissimilar, you can improve compression a bit using specific algorithms designed for this case).

And in any case, the rise in internet bandwidth will far out pace the size of the media.

On a 5mbit connection, getting ideal download speeds, you can download about 2gb/hour.

You can encode a 2560x720 (3D 720p image) content using existing H264 tech at 2gb for 45-60 minutes in high quality (not blu-ray, but much better than DVD). That's practically streaming 3D 720p Video at only 5mbit.

When you're dealing with 20mbit or higher connections, you can stream channels of 1080p 3D content without saturating your network connection.

I doubt anyone will ever need those 93tb 4K lossless compressed source material for home viewing.

I have a lot of experience in this field, and here are the reason why physical media is doomed, probably even sooner than many expect.

Here's why:
1. BluRay licensing makes it very difficult (expensive) to enable mass-adoption.
2. Bandwidth is getting cheaper while high-speed internet is becoming more accessible.
3. DRM is slowly dying.

This will lead to Downloadable HD content which you could stream/burn/transcode to any format you want within the next 2-5 years (on a mass-market scale as we're already seeing this in some fringe markets).

And if the establishment wont move in this direction, piracy will only grow as people want things to be easy and will take the path of least resistance (if DRM is more complicated/unreliable than Piracy, we'll see more content pirates).

The original question was about Windows, not mac/linux, so here's my windows answer:

1. Partition the hard disk into two parts, drive-C: should be about 20gb and the rest goes to drive-D:
2. Do a clean install.
3. Install a VNC app (or enable remote desktop).
4. Setup an application based firewall and pre-approve all applications the end-user may need.
5. Setup icons on the desktop for the most important apps (and shortcuts to important folders such as my documents/my pictures/etc...)
6. This is probably the most important, after everything is working correctly, create an image of partition-C:. Once you have an image of the OS parition if the OS starts to degrade, you always have a solid starting point that doesn't require 4 hours to install (takes about 30min to restore a 20gb image on even slower machines)

Use VNC to help remotely so that you won't have to visit for every little fix.

There are other things you can do, but this is the crux of it.