The rundll32.exe enables to run a 32 bit function exported from a DLL

This could be with malicious intend, the Sircam worm for instance uses rundll32.exe

W32/sircam:

If the worm finds any open network share, it will attempt to copy itself into the Windows directory on the machine with an open share, with the filename rundll32.exe. The original rundll32.exe file is renamed to run32.exe. If this is successful, the worm changes the file autoexec.bat so that it includes a command to run the worm file previously dropped to the C:\recycled directory.

from: http://www.sophos.com/virusinfo/anal...32sircama.html


So check your file, if it is exactly yhe same as on the CD, it is the one from Microsoft...

If you do not trust that app don't allow it. However some other progs or plug-ins need the run32dll otherwise they will not work properly.