I have installed in my computer and running the following software:

PosgresSQL 9.3.2.3
PostGIS 2.1.1.1
QGIS 2.0.1 Dufour (this one installed through the OSGeo4w package)
QGIS 1.7.0 Wroclaw

I am concerned as far as I know that all of them somehow operate, or use, or access or read the GDAL library.

does it mean I must have different versions of GDAL running depending on which one I am using? If I open the OSGeo4W Shell it says GDAL 1.10.1, how can I check the other versions if any?

Perhaps, all of them use only the latest one. Ideally I would like to know how to check this and by which means.