This question has been asked many times and was once again asked today on an internal forum. It is hard to come up with an explicit answer, but I feel I can give you some (personal, non-binding, your mileage may vary, please take with a pinch of salt and don’t sue me) opinions. For SBS 2003 the non-scientific sizing appeared to go like this: “between 2 & 4GB of RAM, depending on number of users”. I often saw a machine for around 25 users with 4GB of RAM and there was headroom. Disk – don’t buy 1.5TB disks, but don’t by 30GB either. Buy largish and try to size data before you make the decision 1 CPU or 2, or perhaps more importantly, a box that can take 1 CPU or 2? The the time SBS 2008 arrived the difference in cost of a 2GB or 4GB box was trivial. Now SBS 2008, if you want to be scientific about it would look something like this: Minimum specs are found at http://www.microsoft.com/sbs/en/us/system-requirements.aspx Think Windows Server 2008 for x users, plus Exchange sizing for x users plus some wiggle for all the SBS 2008 bits, including WSS, Backup. Since working all the above out, I tend to use the following guides: 4GB of RAM for 1 User, 8GB for more than 30 or so, however this is MY opinion and not tested Disk as above, mirrored in h/w (yes, mirrored, not raid 5) Dual core for a starter system going to multi-cpu & multi core for a very busy system The Premium node is sized as any other Windows Server 2008 system SQL or Terminal Services or ISA… etc Now while this might sound very sketchy, I’ve never benchmarked any SBS systems and this is my rule of thumb. I’ve seen some 5-person businesses that stressed a 4GB 2-cpu Xeon SBS 2003 system and I’ve seen 40 people lightly load a 1 cpu, 2GB RAM system. Sizing is not a science and you should always put in more than you need as it is easier for something to be sat idle than to be “in need”. Finally, on the sizing, consider your own system. Put in SBS 2008 for yourself and can use yourself as a reference...