How do I re-configure 3d graphics

I foolishly installed the recommended ATI drivers and was left with a monitor displaying "can't display this resolution: default resolution 1024x768 60Mhz"
Using the terminal I managed to remove the ATI drivers and got back to a 2D desktop (initially the std. 3D install). How do I reinstall / reconfigure the 3D desktop?

 I obtained the following if this helps:

[sudo] password for alan:
  *-display
       description: VGA compatible controller
       product: Manhattan [Mobility Radeon HD 5430 Series]
       vendor: Hynix Semiconductor (Hyundai Electronics)
       physical id: 0
       bus info: pci@0000:02:00.0
       version: 00
       width: 64 bits
       clock: 33MHz
       capabilities: pm pciexpress msi vga_controller bus_master cap_list rom
       configuration: driver=radeon latency=0
       resources: irq:24 memory:c0000000-cfffffff memory:dfac0000-dfadffff ioport:ee00(size=256) memory:dfa00000-dfa1ffff
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 12.04 LTS
Release: 12.04
Codename: precise
Linux alan-desktop 3.2.0-26-generic-pae #41-Ubuntu SMP Thu Jun 14 16:45:14 UTC 2012 i686 athlon i386 GNU/Linux