Hi, linux will be a lot better to use for a server than windows.
Now u need support for the OS?
If so then I would recommend Redhat Linux or SUSE Linux Enterprise.
Redhat
http://www.redhat.com
SUSE Linux Enterprise
http://www.novell.com/linux
Redhat linux and SUSE linux r the best commercial linux distros.
Now if u don't need support and want to use something free then try CentOS
CentOS
http://www.centos.org/
CentOS is actually an open source or free version of Redhat linux also designed just for servers.
Now this isn't linux but its also unix like and that is freeBSD, its servers r very stable and yahoo itself runs on it.
freeBSD
http://www.freebsd.org/
Just make sure u use the 64 bit version for such a powerful machine and for daily use and even for simple server use I would recommend openSUSE cause its my favorite and very easy to use.
http://en.opensuse.org
Linux and Unix work great on intel machines and support all common hardware.