Not fast enough to really be noticeable - 1.8ghz vs 2.4
Do you know the make/model of the motherboard inside the laptop? The laptop's make and model can also be used to find this.
The reason I ask this is because upgrade options may be limited depending on the chipset supported.
HM77, QM77, HM76, HM75, and HM70 all support your current cpu, but what you can go up to may not be worthwhile.