what question to ask?

our office is very small. My boss is veiw other medical software. They are wanting to change to another medical software. I sat in on a demo today. It looked like a DOS mapped over to look like windows. we have windows xp standard on our server with minimum requirement. on our stations we have windows xp professional. What are the question I need to ask to really determin if it will run on our small network. we have 15 station. What is the usual amount charge or a conversion from one medical system data to another?