It sounds like you are not really a systems expert... so my recommendation would be Ubuntu, mainly because of the answers you will be able to find via Google co

It sounds like you are not really a systems expert... so my recommendation would be Ubuntu, mainly because of the answers you will be able to find via Google compared to CentOS. CentOS is a remix of Redhat's server, so support is generally secondhand and also a lot of the community are pretty sysadmin savvy, so you may get lost in the terse explanations and lack of hand holding. On Ubuntu you get a wider audience, a lot of "how to" guides as well as a lot of "what do I do now" discussion forums to glean from. As to the flavor of ubuntu, you will only be doing a few things in the GUI (copy files, maybe a backup program, etc.) most of the meat is accessing and editing the config files via a terminal. I Would go with xubuntu as the GUI is not as resource intensive as the others.