error during simple install of July CTP of SQL Server 2008

I keep getting the following error during the simplest install of the July CTP of SQL Server 2008 (just Database Server and Workstation tools -- nothing else).

The link is useless.

I have Visual Studio 2008 B2 already installed.

I am running Vista.

Any ideas? I can't create a user account with a name that long through Control Panel (User Accounts).

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TITLE: Microsoft SQL Server 2008 Setup

SQL Server Setup failed to execute a command for server configuration. The error was [Microsoft][SQL Server Native Client 10.0][SQL Server]Windows NT user or group 'SAMMAXPC\SQLServerMSSQLUser$SAMMAXPC$MSSQLSERVER' not found. Check the name again.. Refer to the server error logs and Setup logs for detailed error information.

For help, click:http://go.microsoft.com/fwlink?LinkID=20476&ProdName=Microsoft+SQL+Server&ProdVer=10.0.1049.14&EvtSrc=setup.rll&EvtID=29521&EvtType=lib%5codbc_statement.h%40Do_sqlScript%40OdbcStatement%3a%3aexecute_batch%40CnfgSQL%4080%40x3c29

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[1555 byte] By [SamMaxwell] at [2008-1-10]