what you can do is use the root account that already comes with linux, and go to the command prompt and type passwd root and then setup a password for root that you will only know and no one else will probably even know of this account. just setup a password and the root account should appear in the user selection screen now.
now this may work or not, because im telling you this from my knowledge of mac os x, which is based on linux/unix, but it should work anyways.
Core 2 Duo e4500 2.2ghz @ 2.8ghz
evga 650i ultra
2gb 400mhz ram OC'ed to 450
evga geforce 7600GT overclocked