You can definitely install a different OS on that system. Keep in mind that at that point you no longer have OS support (do still have hardware support) from Dell (would have to contact Microsoft), but for most people this isn't a big issue.
Technically, can I reformat and install Windows 2008 R2 Enterprise on a Powervault NX3100?  I understand that the NX3100 is basically just a server with Windows Storage Server but I'm wondering if there is anything that would prevent the installation of regular Windows 2008? Thanks.
Install Windows 2008 R2 Enterprise on NX3100?