What version of Photoshop do you use? I would check out the system requirements for CS4:
http://www.adobe.com/products/photoshop/photoshopextended/systemreqs/?promoid=DRHXH
check out this deal on an HP for an all around good notebook:
http://www.officemax.com/technology/computers/laptop-computers-and-tablet-pcs/product-prod2760030