Do you get any errors when you try to open it?
To open a correctly secured database, you'd have to (a) join the workgroup
which is associated with the file and (b) have a valid user/pass combo. If
you do those two things, you'll be able to open your database. Note that if
you rebuild your workgroup file you must use EXACTLY the same information or
the SID won't be correct, and Access will think it's the wrong workgroup. If
you used the security wizard, the wizard may have saved a copy of this
information for you (search for any files with a .snp extension - that's an
Access snapshot).
You can try re-joining the default system.mdw file (do a file search for
it). You didn't say which version of Access you're using, but basically you
run the Workgroup Administrator utiltiy to rejoin your workgroup.