Inspiron5100/Radeon7500 -only 1024×768!

Hi All,
A recently purchased Inspiron5100 with 16MB ATi Mobility Radeon 7500 – the maximum Display Resolution allowed is only 1024×768!
I have an external 17″ LCD monitor with which i use the notebook, and hence want to increase the resolution tomaybe upto 1280×1024!
The system is preloaded with WinXP-Pro.

Any help would be highly appreciated!Thanks.