Microsoft Symbol Server / Local Cache Hash Algorithm

This page has info on calculating the IDs for the symbol files as well as executables/DLLs.

Basically, for executables and DLLs, you extract the timestamp and filesize from the PE header as listed in the page that Griff linked to. For PDB files however, you will need the DBH command from the Windows Debugging Tools. Simply load the PDB file into DBH and use the INFO command to get the PdbSig/PdbSig70 and PdbAge. Bam! That’s it.

I just created the appropriate folders for the PDB files that I had in my SYSTEM32 folder for some reason, and finally moved them to the local symbol store.

Try looking at this page: Symbol Server Callback Function

EXE/DLL directory name is created by concatenating hex string of the "file modified" time-stamp and "SizeOfImage" from IMAGE_OPTIONAL_HEADER