Unable To Access My Files

I had recently had to reinstall Windows XP. However, after I reinstalled, I could not access or use any of the old software or files that were still on the computer such as microsoft office. When I try to open and use the software, it takes me into the software screen (ie a blank document for word/excel) and it tells me that the software is not installed under the current user and then the program closes down. I also cannot access my documents saved under my user name. When I try to open the folder, it tells
me that I do not have access to it. It will not allow me to edit its name or delete it as well. In addition, it keeps telling me the folder is empty when I right click and look on its properties while at the same when I go up a folder and look under properties, the same folder has 9 megs in it.