Please have a look at my model. I can't perform boolean substraction on it.Could you please prompt on what the problem is?http://www.4shared.com/photo/Ep01Sbdkba/mul_1_.htmlbavdeyka2015-03-06 12:31:27

I guess the first link is faulty, here's a download one: http://www.4shared.com/download/Ep01Sbdkba/mul_1_.dwg?lgfp=3000

What program was used to create the 3D model?What are you trying to extract from the model?

This was created in Solidworks by another person. It won't substract even from primitive blocks, such as box. So I'm sure that the problem is in this model.

Can't you reproduce the 3D model in AutoCAD?

Hello bavdeyka, can you still have the Solidwoks file or can you ask the other person to do a "save as .sat file with the good options" here shown.
maybe if it has be done as a .step or not with the good options you will get surfaces and not solids.
Then you will have to rotate by -90° around Z ( OK with UCS world ) then rotate by +90° around Y ( set a special UCS for this ) your model to have it in AutoCAD with the same way as Solidworks.