can I "merge" 2 DVDs ?

Hi group!

I am using winXP Home and have got 2 DVDs now which I am asked to copy
to one DVD. And I have no experience and have never done that before.
Each of theses DVDs has folders named VIDEO_TS and AUDIO_TS.
The AUDIO_TS is empty and the VIDEO_TS of the 1st DVD has 3 .VOB-files
the 2nd has 9 .VOB-files.
The first 3 VOB-files in each VIDEO_TS-folder have the same names.
Is there an easy way to "merge" these folders and give them an
autostart-file too??

Any help will be appreciated very much, thanks Raimund.