The following bug has been logged online:

Bug reference: 2227
Logged by: Matthias Klein
Email address: matthias (AT) cmklein (DOT) de
PostgreSQL version: 8.1.2
Operating system: Windows XP
Description: Internal account lookup error
Details:

While installing PostgreSQL 8.1.2-1 on my Windows XP Professional machine, I
receive an "Internal account lookup error" (Matching of account names and
security preferences failed) which results in the rollback of the
installation procedure. This is accompanied by a modal dialogue claiming
that a "Fatal Error" made the installation fail.
After this procedure, the postgres-User was created in the systems user
database.
This error was caused every single time I attempted the installation -
whether as normal user or as administrator.

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