I would strongly advise using SQL rather than Access, even if it is SQL Express. If you are going to have multiple users and use this across the enterprise Access is not really suited.
As far as tables I always use effective dating. so on all tables, jobs, personnel, org, benefits, certifications, locations, accounts, etc put a starting and ending date. That way you can leave historical and even future data in our tables and just look for today > startdate and today < endate when looking up records.
I have made some great HR solutions with InfoPath but SQL will be easier to work with (web services) and perform much better down the road. Most company's personnel records would swamp an Access DB pretty quickly.
Checkout
www.infopathdev.com and
www.qdabra.com as resources.