I see from your specs that you have 256MB of RAM. I also assume you are running windows XP. I used to have an older version of AMD Athlon XP. I noted that as time went on with windows XP it uses more and more RAM as you install new software and stuff. Inorder to increase your boot up time, I recommend increasing your RAM to 512MB or higher (1GB is sweet), and trust me you will notice a big difference.
PS - Is your graphics card built-in with shared memory. If so you are currently running on 256MB-64MB, hence they slow boot up and generally slower PC.