I tried to install on XP SP2 and it failed with this error in the event log.
Product: PostgreSQL 8.0-beta1 -- Failed to run initdb: 1!
Please see the logfile in 'C:\Program
Files\PostgreSQL\8.0-beta1\tmp\initdb.log'.
I couldn't find the log file because the installation removed all the files
in that directory.
Geoff