How much money do you have? Windows 2000 Server - which is an old operating system and has been replaced by Windows Server 2003. If you can afford Server 2003, then go for it - its very easy to use, and will do a better job then Linux will ever do (thats in my opinion - but it's a very debated issue).

There are a couple of things we would need to know before you could make a decision:
How fast is its processor?
Your computer can't have 120gb of ram - its limited to 4gb by the x86 architecture. How much ram do you really have?
How big is the hard disk?
What internet connection are you on?
Does your ISP block incoming port 80? (you might need to call them to find out - this question is very important to know before you start)
How computer literate are you? Have you used linux before?

Answer some of those, and we can make a better decision for your specific situation.