I am in need of a bit of assistance. My current laptop (a 17" HP Pavilion, P4 3.2 GHz, 2 GB Ram, OS XP Pro) is in need of replacing. I am considering the 15" 2.4 GHz Macbook Pro and a 15 2.5 GHz Macbook Pro. I plan to use the laptop as a desktop replacement and I mainly do CADD (design) work with 3D modeling and some renderings. What I am wondering is if the differences between the 2.4 and 2.5 GHz configurations will make a noticeable difference in what I am doing. When I look at things based on the technical specs the 2.4 GHz unit is ever so slightly slower (0.1 GHz), has less cache, has a smaller hard drive and has the 256 MB graphics card vs the 512 MB card for the 2.5 GHz configuration. What I am not sure of is if these differences will be noticeable in doing my work and are they worth the additional $500.00 that the 2.5 GHz configuration costs. Also, I have an additional question regarding using the Mac on the internet. On my present laptop (OS - XP Pro) I utilize antivirus software to protect my computer when on the internet/e-mail. Would the Macbook Pro require the same type of antivirus software when used on the internet/e-mail? If so what works the best? Thanks for your comments.