A lot of my readers have tried to use the Synaptics driver on their Dell laptops when they found my post about it. However, some Dell laptops do not have touchpads made by Synaptics. They have Alps touchpads. If you are not sure about what kind of touchpad you have, please see this post about identifying the correct model.
When I helped my user to upgrade his Inspiron 1420 to Windows 7, I used the driver for Vista. Here is the link to the download. This driver is for 32bit only. If this does not work for you, you can also try the driver for Windows 7. Here is the link. The second link provides both 32bit and 64bit drivers.