Protools LE for MAC using an MBOX

[Merc]

I'm currently using a PC but I just purchase an ibook and a friend of mine is trying to sell me his MBOX he baught about 2 months ago and still can't figure it out. He wants to purchase cubase cause he sees how easy I work it and knows that I can show him how to use it. Now I do all my recording in my PC with Cubase which i'm very happy with, however, I would like to have protools as an additional option in my studio. Now I told him that I would need to check it out first and if I liked it, I will buy it from him (only at a good price of course). The problem I have now is that I installed Protools in my mac and plugged the MBOX into the usb. For some reason, when I open protools, it says that it cannot find the hardware or it is in use (-9014). I didn't want to install protools in my pc but I did just to check it out and it installed fine on my pc. Anyone know what I can do to correct this? Thanks in advance!