I recently bought a new laptop to replace my old one (an antique PIII-1100MHz).

I naturally bought one able to run in x64 mode. It was bundled with a professional version of Windows Vista. That's nice, as the home version would have annoyed me, due to the lack of many things that I consider to be mandatory for a sane operating system (real user rights management,...)

As we are in 2007, I naively thought that I should be able to use it in 64bits mode. After all, there was many reports during the Vista development stating that Vista would be bundled with both 32 and 64 bits versions.

The real situation is unfortunately different.
The OEM version pre-installed on my laptop is still a 32bits version, even though the computer is perfectly 64 bits-able. On the positive side, the Vista license agreement (professional version) clearly states that you can use one of those alternative versions of Windows if you want:

*Windows XP media center edition
*Windows XP tablet PC edition
*Windows XP professional
*Windows XP professional x64
*Windows 2000 professional/workstation

Those are the so-called "downgrade" rights granted by Microsoft.

This seems to be a positive thing to me, but I initially thought that I would have no use of it (after all, I already paid for a Vista pro version).

As this laptop only features a 32 bits version pre-installed version, I downloaded a 64 bits version of Vista professional.
Surprise, surprise...
The OEM key of my 32 bits version does not work with a 64 bits version!
I asked Microsoft (in my case Microsoft France) about it, and the reply was that if I was interested by a 64 bits version of Windows Vista, I should ask my usual software retailer about it in order to buy one. In other words, even if I already bought (bundled with the computer) a Vista professional version, I should buy once again a new one in order to have access to the 64 bits version.

A bit pissed (well, more than a bit) about it, I still decided to try installing an x64 version of Windows XP. First task: locate CD/installer. Microsoft silently ignored my question regarding how to obtain a genuine installation CD, so I had to download an ISO image from a peer to peer network.
After installation, I have unfortunately found a big stopper: as my laptop is relatively new, a few drivers were not available for XP x64, including the Nvidia graphic driver.

The unfortunate conclusion is that I had to revert to the 32 bits version of Vista that was bundled with my Laptop.

As I really want a 64 bits able operating system (in order to develop 64bits applications), I decided to download a 64 bits/AMD64 version of the Ubuntu Linux distribution.

It seems that in my case, Microsoft did a really smart marketing/commercial decision leading to:

* an annoyed customer
* a good way to slow down 64 bits adoption
* made me download and try a Linux distribution

Way to go!