You should look at using Volume Shadow copy (Volume Shadow Service / VSS) for open/locked files on WinXP, Win7 or newer recomended, NTFS drives.
NTFS formatted drives are a base level requirement for copying open/locked files like Outlook PST files. If you are not familiar with the differences between FAT(FAT32/FATEX) and NTFS drives then you should do some research now to understand file system locking and management options available.
This is a very good reference for using robocopy to backup open/locked files: http://ithelp.cveg.uark.edu/IT_Help...
If you are running Exchange 2010 and have "good storage space" for all of your Outlook/Exchange users, I strongly recommend importing all PST files to Exchange and not allowing local "c:\" drive PST files. Read more here: PST import request.
I know this is not an explicit answer but I hope it helps you in the right direction for your company. I'm happy to help with the actual details on this topics if you think either reference might be what you are looking for.
message edited by mikewwood