Probably not a vista thing but thought I'd mention it anyway.
There is an ACL issues when trying to install SQL Server Management Studio Express Edtition.
There are a few posts in the SQL forums here:
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Has anyone succeeded in doing a re-install without dropping the existing partition?
I tried and had all sort of weird error messages come up. eg could not connect to Service Account, Off 97 Outlook threw an exceptiom everyime it started etc