Using .dll file compiled in win9x in MATLAB 2013b 32bit

I am trying to run an old MATLAB script that calls upon a Simulink model which in turn calls upon a S-function that is defined as a .dll file. I get the following error message:

Error using run_sim (line 115)
Error while obtaining sizes from MEX S-function 'General_Newmark2' in 'sim_cape/Bridge
Model/Newmark-beta solver/Linear Analysis'.

Caused by:
    Error using run_sim (line 115)
    Invalid MEX-file 'C:\Documents\turky\Desktop\Kopie von Benchmark
    Bridge\General_Newmark2.dll': C:\Documents\turky\Desktop\Kopie von
    Benchmark Bridge\General_Newmark2.dll is not a valid win 32 application.

I do not have the source code of the .dll file.

I am running a 32-bit version of MATLAB 2013b in a VirtualBox Windows XP machine.

Has anyone encountered similar problems and how did you go about solving it?