You need .NET Fra,ework 3.5. I do not have a Windows 7 machine but, it should be built in, you just need to enable it.
Go into programs and features in the Control Panel and click turn windows features on or off and check if its there.
Sorry for my english. I do as follows. I work in Photoshop and I keep a file in a format png. Then I convert a file in a format dds by means of DDS Converter 2.1 I import to game, looks perfectly. Good luck!