I try to install OSGeo4W but when I tried to run it appeared an error message about ippj-5.3.dll is missing... does anyone know what happen?
You can try reinstalling the libjpeg package which will replace the jpeg_osgeo.dll with the non-IPP one. Or you could try removing it.
The solution should be: delete the directory C:\OSGeo4W, start installation again and you should select only the package qgis or qgis-dev, do not click on any other package. Then everything runs as it should