1) Take a backup of all relevant files before making any modifications. This
applies to all mods, not just security mods. If you don't then you're not
"professional".
2) Obtain the Security FAQ and/or experiment with security on sample databases
until you feel comfortable with it. This applies to all aspects of
programming.
3) If you don't know what files might be affected, backup whole folders so you
can restore them (in some cases, this might not be enough, play on a backup
computer)
4) You said you were "messing around". That's fine, on a sample or backup
system.
5) Best way to delete security is by restoring original *beforehand*.
Otherwise, the Security FAQ says how to remove security.
6) Do not proceed further without the Security FAQ. Do not rely on
pre-conceived understandings of security. Access security has the best
facilities available (within context), but you need to understand it first.
That means experiment on a backup or sample system.
Chris