It's worth noting that starting Steam as an administrator will take care of a lot of different problems for the initial launch of Operation Arrowhead.

More specifically about the DirectX part: If you're getting various error messages about DirectX components missing (particularly X3DAudio1_6.dll), or Steam tries to install DirectX perpetually, try installing the latest version of DirectX. If that doesn't work, you may want to install the DirectX 9 Redistributable from here as well: http://download.microsoft.com/downlo...009_redist.exe

"Stephen Wolfram is the creator of Mathematica and is widely regarded as the most important innovator in scientific and technical computing today." - Stephen Wolfram