In my Qt install on Windows the core libraries are QtCore4.dll at 2.3 MB and QtGui4.dll at 9.1 MB for a total of 11.3 MB. When you package them for distribution with something like NSIS and the lzma compression they come down to slightly smaller than 4 MB. Sure they take up the same space when unpacked but they are hardly a major imposition for the utility they provide. They are much smaller than the Java runtime that Jambi will also require on the target machine. To make the installed size smaller see the upx suggestion above.