Branden,
Len is on the money! Some of the other posts, while well intended, may have mis-represented some facts, or written them in a way that could be mis-interpreted. The posters may not have noticed your footenote that you are using AC97.
Access & Access security
can do what you are asking, but it is not the be-all and end-all. If security is "mission critical", Access is not the best place for your data, as there are numerous offerings on the web that can enable the willing to get to your data, assuming their network permissions are such that they have read permission on the file.
That said, here are the steps you need to take.
1) Get the FAQs.
http://support.microsoft.com/default.aspx?scid=/support/access/content/secfaq.asp#_Toc493299666
2) Read the FAQs
3) Re-read the FAQs
4) Follow the step-by-step instructions in the FAQs very carefully and to the letter - do this as a trial run at least once, on a test database.
5) Ensure you take a back up copy of your production database, before you start "messing with" security
No, I am not trying to be cheeky, or imply any level of ability on anyone's part. Access security is difficult to get right, and it is very easy to mis-understand and "implement" incorrectly. Conversely, it takes a some understanding, learning, and experience to implement correctly.
Your statements, above, are indicative of an incorrect implementation of Access security.
Point #32 in the linked FAQ above, deals with one of your questions.
32. I thought I helped protect the security of my database, but someone opened it with his or her own workgroup file. Is Microsoft Access security broken?
When implemented correctly, it is very good for keeping out all but those with serious intent, and keeping sets of users (groups) on the straight and narrow.
HTH
Regards
John