DirectX 10 has been around for a while now, but up until recently it was only available via Microsoft's Windows Vista operating system and was not compatible with its predecessor, Windows XP. More recently, however, a company called Falling Leaf systems announced what it called the 'Alky Project' - an alpha release of the DirectX 10 API which, it claimed would bring DirectX 10 gaming from the confines of Vista and onto users' systems who still ran XP, and later it promised Linux and finally onto OS X.
It had previously been touted that Crysis would be a DirectX 10 exclusive. However, those fears were unfounded and Crysis - like so many other Direct X 10 games - runs perfectly happily under the older API, with the only drawback being that the older version doesn't take advantage of some of the newer DirectX 10 features.
There are some graphics cards that didn't support Direct X 10 features, such as Nvidia's 7000 series of graphics cards. This meant that gamers would face the prospect of not only having to upgrade their entire operating system, but also their graphics hardware. Meaning that to play a £30 title, gamers would be looking at upgrades averaging £140 in order to make their system compliant.
Currently, there's only a handful of games which are DirectX 10 exclusive, and it's likely that games developers will likely still dictate the market as well as the API their games will run on; after all, from a business perspective, it makes sense to sell millions of copies to a mass market rather than a few thousand in a niche market. Windows XP is still the operating system of choice for many gamers due to the performance and compatibility issues that have blighted Vista. DirectX 10 and Vista need to offer more to encourage gamers to make the switch.
The developers behind Crysis had previously come under fire for disabling the 'very high' visual settings in Crytek, considered by many to be the most visually advanced game available. The 'very high' settings are only available to gamers using DirectX 10 and some believed this was an attempt to coerce gamers away from XP and onto Vista. However, it was later discovered that it was possible to enable the maximum settings under Direct X 9.0c with a little tweaking of the games configuration files, with the result that the different versions weren't so different after all, save a few subtle visual elements only achievable under DirectX 10.
However, it seems unlikely that games developers will commit corporate suicide by developing Vista-only titles. Unless Microsoft begins waving huge wads of cash under the developer's noses, gamers are unlikely to feel the need to jump ship towards Vista and DirectX 10. In fact, it is more likely that - and has been rumoured for some time - Microsoft will relent and release a diluted version of DirectX 10 for XP. But for now, it's business as usual for gamers and Windows XP.