補足説明
Display Driverの検索するAMDのhomeは、下記です。(Linux x86, motherboard, Radeon Xpress 200)
http://support.amd.com/us/gpudownload/Pages/index.aspx

あのあとsudo sh ati-driver-installer-9-3-x86.x86_64.run --buildandinstallpkg Ubuntu/9.04
で起動してみたらドライバーは入ったのですが今度はエラーが出てきます
下にログを載せておいたのですが結局セーフグラフィックモードになってしまいます
何とかならないでしょうか↓↓

X.Org X Server 1.6.0
Release Date: 2009-2-25
X Protocol Version 11, Revision 0
Build Operating System: Linux 2.6.24-23-server i686 Ubuntu
Current Operating System: Linux *****-desktop 2.6.28-15-generic #52-Ubuntu SMP Wed Sep 9 10:49:34 UTC 2009 i686
Build Date: 09 April 2009  02:10:02AM
xorg-server 2:1.6.0-0ubuntu14 ([email protected])
    Before reporting problems, check http://wiki.x.org
    to make sure that you have the latest version.
Markers: (--) probed, (**) from config file, (==) default setting,
    (++) from command line, (!!) notice, (II) informational,
    (WW) warning, (EE) error, (NI) not implemented, (??) unknown.
(==) Log file: "/var/log/Xorg.0.log", Time: Wed Oct 14 23:28:07 2009
(==) Using config file: "/etc/X11/xorg.conf"
(==) ServerLayout "aticonfig Layout"
(**) |-->Screen "screen1" (0)
(**) |   |-->Monitor "monitor1"
(**) |   |-->Device "device1"
(==) Automatically adding devices
(==) Automatically enabling devices
(WW) The directory "/usr/share/fonts/X11/cyrillic" does not exist.
    Entry deleted from font path.
(==) FontPath set to:
    /usr/share/fonts/X11/misc,
    /usr/share/fonts/X11/100dpi/:unscaled,
    /usr/share/fonts/X11/75dpi/:unscaled,
    /usr/share/fonts/X11/Type1,
    /usr/share/fonts/X11/100dpi,
    /usr/share/fonts/X11/75dpi,
    /var/lib/defoma/x-ttcidfont-conf.d/dirs/TrueType,
    built-ins
(==) ModulePath set to "/usr/lib/xorg/modules"
(II) Cannot locate a core pointer device.
(II) Cannot locate a core keyboard device.
(II) The server relies on HAL to provide the list of input devices.
    If no devices become available, reconfigure HAL or disable AllowEmptyInput.
(II) Loader magic: 0x3bc0
(II) Module ABI versions:
    X.Org ANSI C Emulation: 0.4
    X.Org Video Driver: 5.0
    X.Org XInput driver : 4.0
    X.Org Server Extension : 2.0
(II) Loader running on linux
(++) using VT number 7

(--) PCI:*(0@1:5:0) ATI Technologies Inc RS400 [Radeon Xpress 200] rev 0, Mem @ 0xc0000000/268435456, 0xb0100000/65536, I/O @ 0x00009000/256, BIOS @ 0x????????/131072
(II) Open ACPI successful (/var/run/acpid.socket)
(II) System resource ranges:
    [0] -1    0    0xffffffff - 0xffffffff (0x1) MX[b]
    [1] -1    0    0x000f0000 - 0x000fffff (0x10000) MX[b]
    [2] -1    0    0x000c0000 - 0x000effff (0x30000) MX[b]
    [3] -1    0    0x00000000 - 0x0009ffff (0xa0000) MX[b]
    [4] -1    0    0x0000ffff - 0x0000ffff (0x1) IX[b]
    [5] -1    0    0x00000000 - 0x00000000 (0x1) IX[b]
(II) "extmod" will be loaded by default.
(II) "dbe" will be loaded by default.
(II) "glx" will be loaded by default.
(II) "record" will be loaded by default.
(II) "dri" will be loaded by default.
(II) "dri2" will be loaded by default.
(II) LoadModule: "extmod"
(II) Loading /usr/lib/xorg/modules/extensions//libextmod.so
(II) Module extmod: vendor="X.Org Foundation"
    compiled for 1.6.0, module version = 1.0.0
    Module class: X.Org Server Extension
    ABI class: X.Org Server Extension, version 2.0
(II) Loading extension MIT-SCREEN-SAVER
(II) Loading extension XFree86-VidModeExtension
(II) Loading extension XFree86-DGA
(II) Loading extension DPMS
(II) Loading extension XVideo
(II) Loading extension XVideo-MotionCompensation
(II) Loading extension X-Resource
(II) LoadModule: "dbe"
(II) Loading /usr/lib/xorg/modules/extensions//libdbe.so
(II) Module dbe: vendor="X.Org Foundation"
    compiled for 1.6.0, module version = 1.0.0
    Module class: X.Org Server Extension
    ABI class: X.Org Server Extension, version 2.0
(II) Loading extension DOUBLE-BUFFER
(II) LoadModule: "glx"
(II) Loading /usr/lib/xorg/modules/extensions//libglx.so
dlopen: /usr/lib/xorg/modules/extensions//libglx.so: undefined symbol: miInitVisualsProc
(EE) Failed to load /usr/lib/xorg/modules/extensions//libglx.so
(II) UnloadModule: "glx"
(EE) Failed to load module "glx" (loader failed, 7)
(II) LoadModule: "record"
(II) Loading /usr/lib/xorg/modules/extensions//librecord.so
(II) Module record: vendor="X.Org Foundation"
    compiled for 1.6.0, module version = 1.13.0
    Module class: X.Org Server Extension
    ABI class: X.Org Server Extension, version 2.0
(II) Loading extension RECORD
(II) LoadModule: "dri"
(II) Loading /usr/lib/xorg/modules/extensions//libdri.so
(II) Module dri: vendor="X.Org Foundation"
    compiled for 7.4.0, module version = 1.0.0
(II) Loading extension XFree86-DRI
(II) LoadModule: "dri2"
(II) Loading /usr/lib/xorg/modules/extensions//libdri2.so
(II) Module dri2: vendor="X.Org Foundation"
    compiled for 1.6.0, module version = 1.0.0
    ABI class: X.Org Server Extension, version 2.0
(II) Loading extension DRI2
(II) LoadModule: "fglrx"
(II) Loading /usr/lib/xorg/modules/drivers//fglrx_drv.so
(II) Module fglrx: vendor="FireGL - ATI Technologies Inc."
    compiled for 1.4.99.906, module version = 8.59.2
    Module class: X.Org Video Driver
[atiddxSetup] X version mismatch - detected X.org 7.1.0.0, required X.org 7.4.-1.906
(II) UnloadModule: "fglrx"
(II) Unloading /usr/lib/xorg/modules/drivers//fglrx_drv.so
(EE) Failed to load module "fglrx" (module requirement mismatch, 0)
(EE) No drivers available.

Fatal server error:
no screens found

Please consult the The X.Org Foundation support
     at http://wiki.x.org
for help.
Please also check the log file at "/var/log/Xorg.0.log" for additional information.

ddxSigGiveUp: Closing log

ATI Catalyst 9.4以降は、R300-R500をサポートしていないので、
taka_aquaさんが試されているように、RS400ではCatalyst 9.3を使うしかないのですが、
Catalyst 9.3のリリース日はUbuntu 9.04のリリース日の前になっているので、
Ubuntu 9.04では上手く動かないでしょう。
Catalyst(fglrx)ドライバを使いたい場合は、Ubuntu 8.04またはUbuntu 8.10を使用するしかないようです。

ただ、CatalystでR300-R500のサポートをやめたのには、フリーなドライバでのR300-R500サポートが進んできたという事情があります。
そこで、フリーなドライバを使用してみるのはどうでしょうか。

radeon xpress 200(RS400)で検証ができないので、確実なことは言えませんが、
Ubuntu 9.10のBeta版のLiveCDやLiveUSBを使って、希望の解像度に設定できるか試してみてはいかがでしょう。

または、9.04でPPAのドライバを使用するという方法もありますが、
https://launchpad.net/~ubuntu-x-swat/+archive/x-updates/?field.series_filter=jaunty
9.10で使用できる見込みがあるなら、正式リリースまで待ってから9.10に移行するのが簡単でしょう。