DirectX 10 was not directly available on the Microsoft Downloads section and here is the news that DirectX 11 would be coming out soon. Get ready to download DirectX 11 soon because its going to feature a better real time experiance. Dont expect some Real Girls coming out of your screens but a better rendering of images and videos making you get a better gaming experiance.
I did a quick search on the Microsoft Downloads section and could not find any official version of Direct X available for download but a google search resulted in some unofficial source which are offering the download links. Lets hope that the downloads are available asap and everyone can experiance better , but i strongly feel that the Direct X11 would be announced with the upcoming Windows 7 operating system by Microsoft.
Check out this Direct X10 vs Direct X11 Video Comparision from Nvidia :
DirectX 11 for Windows XP & Vista Announced Video!
get me a directx11