Today I would like to mention about graphviz command line in windows XP.
You can use each binary executable at \bin folder. For example for dot.exe and given input.gv file, you can produce pdf,png,jpg outputs as follows;
PNG : dot -Tpng input.gv -o out.png
JPG : dot -Tjpg input.gv -o out.jpg
PDF : dot -Tpdf input.gv -o out.pdf
This is useful since you can easily show your random graphs in hierarchical layout.