Because there is no support for yours in the driver
. From the release notes for the Catalyst 11.2,
The following notebooks are not compatible with this release:
- Any notebook launched after this driver release
- Switchable Graphics enabled notebooks using Intel® chipsets.
- Toshiba® notebooks (please contact the notebook OEM for driver support for these notebooks)
- Sony® VAIO® notebooks (please contact the notebook OEM for driver support for these notebooks)
- Panasonic® notebooks (please contact the notebook OEM for driver support for these notebooks)
Toshiba is one of the few that won't allow for the reference AMD drivers
to be installed (same would apply if it had a Nvidia card in it as well).
One reason for that is if yours has the switchable graphics as mentioned in the above, which with yours having the i3 330M in it is likely. If it does in a lot of cases if the reference driver can be installed the switching won't work and requires both the AMD (or Nvidia if equipped) and Intel graphics drivers to be installed, and only the ones from the laptop manufacturer have been made to work with it.