So far I was using the Single Threaded Run Time Library and had no trouble with Boost, however I switched to useing the Run Time Versions just now and found that nothing seemed to work and the error that I get is: "Boost_Regex_vc7_mdid.dll was not found. Re-installing the application may fix this problem" However, the instructions on the website state : "Finally when you use regex++ it is only necessary for you to add the <boost> root directory to your list of include directories for that project. It is not necessary for you to manually add a .lib file to the project; the headers will automatically select the correct .lib file for your build mode and tell the linker to include it. " Im using VC7, and I cant understand why I get this error, do I need to change some setting while linking to the multi threaded versions? For now, I copied the two dll's _boost_regex_vc7_mdid.dll and _boost_regex_vc7_mdi.dll to my working directory and I have a working application, but Im foxed and I would like to know what im doing wrong! Thanks. "Zeros Bits and Bytes"