Only some files were found

Hello All :
I’m new to this. I’m ok at using computers and I know more than the average bear but I am not too familiar with external hard drives.  Recently, I had to hand my computer back in to my school and they give it back totally wiped with a new O/S on it.  I had Windows XP before and now I have Windows 7.   I opened up my hard drive after having backed everything up from the previous laptop and went to put everything back to it’s place today.  Well, I can only find certain files.  The MOST IMPORTANT files of course, cannot be found.  They are just word documents and pictures but they are not to be found anywhere.  When I opened them up I retrieved both the c and d drive and restored them to their original locations and then once I couldn’t find them , tried retrieving them all to a restored folder.  I can’t find about 1500 pictures from the last 5 years of my life or an important document that I need to submit for school.  Any help? Why can I find some things but not these things? I’m freaking out a little bit…of course, so any help in any form is greatly appreciated.  When I backed them up I chose to back up every file on my computer so I’m confused why they wouldn’t be there.
Thanks again,