Switching OS versions can cause all kinds of driver issues for devices originally released with an older OS. The drivers may not always work as advertised.
With most Dell computers, there is a specific order to install drivers - How to Download and Install Drivers in the Correct Order.
Also, when choosing drivers, you may not be able to use the Windows 7 64 bit drivers. If you have a 32 bit OS, use the Windows Vista drivers (I believe you need the Synaptic drivers for that laptop).
Lastly, make sure you have all the Windows updates.