Disclaimer: Do not do this on a production server. Do not do this to any database that you care about. If you want to play, do so on a SQL instance installed on your workstation.
Right, now that's out of the way...
Take the database offline, open the mdf file in a hex editor. Go to an offset 40k or so into the file (to avoid the critical header pages) and then 0 out a block of data. Save the file, close it, go back to SQL and attempt to bring the database online
I say attempt, because last time I tried that, I fried the DB so badly that SQL couldn't bring it back online.
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)SQL In The Wild
: Discussions on DB performance with occasional diversions into recoverability
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We stand on the bridge and no one may pass