Hardware Configuration Opinions

hello everyone, i am looking for user opinions on some stuff here, my server which i am setting up has a 2.8GHz processor with 1GB ram (max 4GB supported) on top of that my "uplink" to the internet is about 526KB/s, i have several HDDs to choose from but i am lingering around a couple of the smaller ones, i have the options of useing software raid 0 on the 40GB HDD with the 80GB HDD but i dont have a redundancy system for backups, i could go with the a software raid 1 with the same HDDs but i would be limited to 40GB space, ulternatly i could set the system up with no raid configuration, either 40GB, 80GB, or a combination of 8.5GB (system) and either the 40GB or 80GB (users), this delema of mine has boggled my mind for the past 24 hours so here i am looking at this community for your opinions on what you would do in the same situation.