I have built a site 4 months ago, and my site is all about streaming movies. I never expected the number of people to jump from 20 to a 100 or more visitors a day. Now I need serious help because the way i built my site is the movie will be watch as it downloads. Basically, my dedicated server is overloaded, and the movie keeps on buffering. It seems that the movie plays faster than it downloads. I have already about 1 terabyte of content on the site, and i do not want to lose any of it.
Is there a way to optimize the server so that the movies play smoothly? It is on a dedicated server. I seriously need help; I am willing to pay for help. I am really desperate as I am getting about 500 visitors every day.

My dedicated server stats are:

Processor: Intel(R) Core(TM)2 CPU 6420 @ 2.13 GHz 2.13GHz
Memory (RAM): 3.25 GB
System Type: 32-bit Operating System
Windows Server 2008
Service Pack 2

I have 1500 Gb of bandwith

Please i need help! is there a way to stream my movies without losing all my datas? or any other ways to make the movies play smoothly?