My computer is also close to 2006 but if I remember well I bought it only in 2007 even if it's a model from 2006.

I have an Intel Xeon dual core 3Ghz, 2Gb ram, Radeon HD 5770. I had right before a Radeon X1900. With the 5770 it's very fine but with the X1900 It was just from good to ok in the demo. Also now I play on Mac which should be slower but with 4Gb ram and it runs very well too.

According to this thread your graphic card should be fine:
http://social.bioware.com/forum/1/to…/index/6239823

The CPU non dual core could be the problem. Try the demo if it is very good this should be fine. For load time I feel DA2 improved that significantly.

EDIT: And take care the minimal OS is XP 32bit with SP3, it's the system I used when I played the demo and a part of the full game on Windows.