Hi,
Step by step (windows7 64bit):
download the file SweetHome3D-4.0.jar and save in to Folder "C:\Program Files (x86)\SweetHome3D\"
right mouse Key on Desktop -> new text file -> start.txt
rename start.txt into start.bat
edit the file and write the following into:
@echo off
{Java -Xmx4096m -jar "C:\Program Files (x86)\SweetHome3D\SweetHome3D-4.0.jar"}
exit
(between the {..} have to be in one line and without { }.)
save the file.
redy!
double-click this file and sweet home starts.