According to ProcessLibrary.com:It's located on the XP Install CD as \I386\DCIMAN32.DL_, a compressed file. See here for directions to expand the file from the CD to your hard drive:dciman32.dll is a module for the Display Control Interface (DCI) Manager. It is used to improve graphics performance as a result of direct video memory access.
dciman32.dll is a system process that is needed for your Windows system to work properly. It should not be removed.
How to expand Windows XP files from the installation disk
It may also be in C:\Windows\system32\dllcache. If so, you can copy it from there to C:\Windows\system32 which it where is runs from.