Here is a link to the ArchiCADWiki page that addresses some installation issues:
http://www.archicadwiki.com/FrontPage?action=fullsearch&context=180&value=install&titlesearch=Titles
See if there is anything helpful there.
Also, are you installing from a disk or from a downloaded package? If the disk is faulty, try downloading from MyArchicad.com. If youare installing from a package you already downloaded, try downloading it again.
HTH