Depending on how Window 7 was installed, you may not be able to recover the old data. The following process will help you find out if your old data is still present, and if it is how to recover it. Firstly you need to set Windows to show hidden files, for details of how to do that see http://www.bleepingcomputer.com/tutorials/tutorial151.html Firefox stores user data such as bookmarks in the profile folder, as you have re-installed Firefox it will have created a new profile folder in Windows 7. You now need to search your computer to see if the old profile folder is still present. Search your entire computer for a file called places.sqlite, you will find at least one copy of this file in your current profile folder. For details of the location of your current profile folder see [https://support.mozilla.com/kb/Profiles]. If you find more than one copy of places.sqlite, you will possibly have found your old profile folder. If you are not sure if you have found the old profile folder, post here giving details of the full paths of where you found the places.sqlite files. You can copy the data from the old profile folder into the current profile folder, for details of the files to copy see https://support.mozilla.com/kb/Recovering+important+data+from+an+old+profile