If you are installing QGIS via OSGeo installer on a windows 64 bit OS (XP, vista or 7), does it install a 32 bits or 64 bit version of QGIS?
Usually the standalone installer installs a 32 bits version, so I want to use the full potential of my new computer (win 7 64 bits, 16 Mb of Ram).
64-bit support has to be compiled separately against 64-bit librarys. Currently, there are no 64-bit packages in the osgeo4w Installer list. The 32bit version runs fine with Windows 7.
Since QGIS 2.0, there is a 64bit installer as well. It installs into C:\OSGeo4W64\ and lives happily next to a 32bit installation under C:\OSGeo4W\. They share the same plugins in C:\user\.qgis2\python\plugins.
Unfortunately, the 64bit is more likely to crash or behave strange than the 32 bit one.
As of August 2013, there a 64-bit version of OSGeo4w. It is currently in Experimental mode, but includes a 64-bit version of QGIS and GRASS, among other features.
