As a follow-up to an earlier post, I should mention that part of the reason I had healthcare data on my personal laptop was to do some data analysis with MySQL. Between MySQL and the command line tools, it was very easy for me to load data from other sources and run queries to monitor or predict the amount of medication we were packaging.
When I was done doing the data analysis, I wanted to scrub the data off my hard drive. On the version of MySQL that was installed via Synaptic on Ubuntu 8.10, the default database engine was MyISAM. When a table is dropped, it deletes the MyISAM file. No need to worry about deleted records retaining data in a "tablespace" file that one might have to worry about in other RDBMSs.
Then all I had to do was scrub the hard drive as I described in my earlier post.