I just followed your instructions and put a password on it.
Thanks!
Yeah!!!
There is one more thing you can do, if you want just a bit more piece of mind. You've already done the most important bit, and you can stop there, but this just finishes the job.
I'm also a single user system, but I have two accounts set up.
The one I use daily is a "Standard" account. It has no administrative privileges. I also have an Administrative account I call "Trouble". It is set to Administer the computer.
On a daily basis I am in my Standard account. Several times a day I do something that requires administer privileges, and it pops up a little box that asks me to "authenticate" myself. At first it might seem like a bit of a pain, but I figure it gives me two protections.
1) Just in case I ever do download a working malware it will only inherit non-admin privileges, it won't be able to do anything serious without 1st asking for authentication - which would alert me that there is something happening that shouldn't be. This is a rare scenario though, and not the main reason I don't run as an admin...
2) As you get to know OS X it gets tempting to fiddle with the system, and fiddling with the system can cause "issues" if you don't do it correctly. A Standard user is limited to how much damage they can do, and the "Authentication" dialogue is a reminder to myself that I am walking on thin-ice, to be careful, to have a backup, to not get distracted, etc etc It's like having a string on your finger to remind yourself of something. The string doesn't do the 'remembering' - it merely tells that there is something to be 'remembered'. The same way that the needing to type the admin user and password reminds me to be careful.
Hope this helps.