Well, there are a lot of problems that you can run into by using a workstation as a server. I'll start off with a few of the basics and then get into things that are a little more complicated. Lets say you use a workstation as your central data storage point, it's a workstation so there is always going to be the temptation to keep using it as a workstation. So what happens when said workstation gets a virus. Take it to a local computer shop and let them wipe and reload it and potentially lose all of your organizations data? Lets hope not. Secondly, workstation operating systems such was windows xp professional only support a certain number of concurrent connections. Meaning that only so many computers can access them at any given time as per license limitations. So if your network is large enough or gets large enough you'll run into issues actually being able to access the files due to these restrictions. Server hardware (provided you get a reputable brand) is way more reliable than workstation hardware for the simple fact that it is designed to run 24/7 where a workstation may not be. Servers typically come with hot swapable hard drives, RAID, and can include other nifty features such has hot swap power supplies, fans and other things. All of these are good to have if you're trusting your organization to a piece of computer hardware. Down time means loss of revenue not to mention the expense of having the computer repaired so it's best to spend a little more up front and get something that will be better. With a server you can also begin to exercise more control over what goes on on our network and workstations. For example if you run a windows environment and have a domain you can setup policies that determine what users have rights to do on their individual workstations which can all be managed from one central location (the server). Really, it depends what your needs are. So more information would allow me to help you better.