Modular 3, 4-axis Bi-polar Chopper Driver Help

I want to build the 4 amp 48v driver and parallel card on Steve
Blackmore's website http://www.pilotltd.net/cnc.htm his design is
based off of Hans Wedemeyer's design http://www.hans-w.com/cnc.htm

1.) Can these drivers fry my motherboard, if so what can I do to
prevent it?
2.) What would be a good power supply?
3.) Should I use a separate motor power supply for each axis?
4.) Are there any design changes I should make?

I'm not an electrical engineer and I have a lot more time then
money right now so any advice is much appreciated.

Thanks