Max dual-boxage?

Folks;

A friend of mine told me about dual boxing (I'm actually running both accounts on the same system). I can run 2 accounts at the same time easily with little to no lag (thus far). I've only got my pair of gnome mages up to lvl 11 right now, but this was my first ever dual-boxing experiment. How many can you run on a given system? I have a HP DV9700 Laptop with a 256 Mb video card (8400 series NVidia, IIRC) and 2 GB system RAM. My fps solo is around 45-60. My fps with 2 accounts running is in the mid to high 30s.

Also, how do you gift levels? I'm thinking of taking these guys up to 60 and then gifting my druid (25 atm) up a ways.

If you are willing to set lowest possible settings, I bet you could actually 5 box on that system. The processor would be good to know, though.

AMD Athlon(TM) X2 Dual-Core Processor for Notebook PCs QL-60 (1.9GHz)
2 Gb RAM
256 Mb NVidia 8400 M graphics card
Windows Vista (no choice there. :-( ) 32 bit

I'm using 2.33 intel core 2 duo, 3gb ram, 128mb dedicated graphics. It's a mac. But I run 3 boxes without any issues at all. Back in the day when I only had 2gb ram I was running 5 boxes without any problems outside major cities.