No Server OS is (or ever will be) supported by Dell on any client system (and vice versa).  That doesn't mean it won't work, just that it might not work, and it is up to you to find the appropriate drivers and make it work.  Drivers for XP will "usually" work for 2003.  If not, then going to the individual device manufacturers' websites for drivers would be the best way to go.  While I have never done this on a 270, I have done it on many workstations ... it "should" be possible.  Give it a go and let us know where you run into problems.
I'm looking to install Windows Server 2003 on an old Optiplex GX270 I was able to obtain from my aunt so i can learn more about how to use the server and possibly run one in my house to see what it can do for me. The only drivers I can fine for it are XP though, has anyone successfully installed 2K3 on theirs, or know someone who has?
Installing W2K3 on GX270