problem with video on installed Ubuntu but not on Live CD and server software ?

[blackmon4627 at bellsouth.net]

I am trying to install Ubuntu on a Compaq Proliant 600 mhz 800 series server. I can run Ubuntu from the live cd with no problem. I am actually impressed with it. But when I tried to install it I got a really poor screen resolution. Is there a workaround for this. I think it is using the ATI Rage chipset but I am a Windows person and do not know how to change drivers etc under LINUX. I am also wanting to use this server for what it is for... a server. What software would you suggest both for allowing it to serve files via the LAN and or Online and for security so I do not get hacked.