To those like me having a hell of a time trying to install PSO2 on their PC, I recommend this very insightfull article from Eliot Lefebvre :

First Impressions: Phantasy Star Online 2’s technical clownshow mangled its PC launch

The title says it all, but on the added benefit of venting our frustration, it gives a lot of hints as to why your install is not working and may help in fixing it.