I came across a post on comp.soft-sys.stat.spss in which the purchaser of a new Dell system with Vista Home Premium edition was unable to install SPSS 13, 14, or 15. They indicate that they spoke to SPSS support, who told them that none of the versions which require activation will install on Vista.
In a follow up message, it was noted that SPSS was working on a patch and that the estimated date of release is the end of April, 2007.
Followup: SPSS has released a hotfix to address the problem. It can be downloaded from the SPSS Support Website (login required — you can use user: guest/password: guest). In addition to the hotfix, the page also identifies the procedure for installing SPSS 15 on Visita.