I bought my current laptop (see signature below) for business use. MSOffice, Visual Studio, SQL Server, etc... I got the cheapest core i-series Intel machine I could find. I figured as long as I stayed Intel with a modern processor I should be okay. This was not intended to be my PT rig, but I figured what the heck, I'll try it. If it doesn't work I've lost nothing since this is already paying for itself as my work computer. I don't "work" in the audio industry; it's a hobby for me.
This laptop is not Avid qualified or approved. It's using the Intel integrated graphics of the i3 chip which is supposed to be a no-no. And I don't know that any i3's are approved. I do see some Core 2 Duos on the list though, and just about any i3 will out perform just about any Core 2 Duo so I figured it was worth a try.
Well, my system is no powerhouse by any stretch of the imagination, but I can record 16 simultaneous tracks from my Mackie Onyx 1640i mixer at a 32 sample buffer for over an hour with no problems or glitches. I can also mix sessions with 20+ tracks without a problem. But I must admit I don't use a whole lot of plugins.
I still plan to get a dedicated Pro Tools rig at some point, but this one was basically free to me since it was just laying around when I wasn't using it for work. I say give it a try. What have you got to lose? If it doesn't work you can always build or buy a qualified system.