I've been using 6.6 Pro for a few years with no issues. Very good product. I just upgraded to 7.1 Pro for achieve compatibility with newer ACAD versions. The computer is a Pentium 4, 2.53GHz, 1GB ram, running XP Pro V.3. The video card is a NVIDIA GeForce 7300GT running dual monitors. The 7.1 Pro so...