Problem with picking fonts from MS office in AutoCAD MEP 2010

When I open drawings created by others, I get a message " Specify font for Style OPT and "Arial Unicode MS" and a host of other fonts appear in the table. If I substitute this with Arial from the drop down list then the drawing opens. I believe Auto Cad automatically picks up either the SHX files in its own font directory or font files from MS office. My computer has Arial Unicode files in C:/Windows /Font directory and I do not know why it is not picking up the font from that file. Please help if you have had similar issue and found a solution.