@ xpi0t0s: Thanks for your reply. Sorry I couldn`t iclude a link to my last post. OLE for Process Control is the old expansion. But what I read so far, is that today no expension is used for "OPC" server.

The best introduction to OPC I found is located here:
codeproject.com/KB/COM/opctechnology.aspx

And another source is the "OPC Foundation"

opcfoundation.org/Default.aspx/01_about/01_whatis.asp?MID=AboutOPC

Daniel