Creating a linux based lan?

[Energize]

At a local charity I volunteer at, the network is in a bit of a disarray; currently I've got a Centos 6.4 box running as a file, web and database server for the lan, which mainly run windows XP. However users continue to save files to my documents or the desktop etc instead of the encrypted staff file share on the server, and recently there has been a spate of spyware infecting some of the PC's which I had to clear up. Not to mention how slow the xp machines have become over time...

So I thought maybe a good solution would be to switch the client PC's to a Linux OS and setup the server as a domain so that each user can have their own desktop mirrored onto whatever machine they go on?

They use Microsoft exchange I believe as an email client, would it be possible to setup an exchange server (or similar) on the Centos box so that users could access their email through their client as usual once they've logged on?

 

[Energize]

The problem is windows server costs money and I don't have another physical server to put it on.

They only use the internet browser, email client and basic office software, I'm sure even they can manage to use a distribution that mirrors the look of windows xp.

Never mind the malware issues that are so prevalent with Windows that I want to prevent, and the lack of os updates.

 

[Energize]

Yes, all software needs to be local as the internet connection is not reliable being on a farm pretty much in the middle of nowhere. I even installed a UPS on the server because of power cuts.