overwrite outlook 2k pst files

i have a user that decided to backup her e-mail on occasion. what she did was copy the pst files (she has 6 – each around 150megs) onto a network drive every once in a while to act as a backup.
this happened agian last night and i got a call this morning. what she had done was move things the wrong way and wiped out the last two weeks of mail.

is there any way to recover from this?
i think im up a creek without a paddle – as the pseudo-techie here i am responsible for all computer related problems regardless of what caused them. i freely acknowledge that i do not know everything and perhaps someone has a trick up their sleeve.

btw ive ordered an external hard drive for a one touch backup but that doesnt pull my ass out of the fire right now.