Assuming you registered the application originally, Adobe should be able to send you your serial number. You can contact them through the links on the bar at the top of these pages.
Assuming you installed without a complete format of your drive search for .prel files and see if you stored your videos in the same folder. If that doesn't help you will need to do a search for video file types (eg .avi, .mpg. .dv, .mov) or a part of the filename that you can remember.
Insanity is hereditary, you get it from your children
As Neale suggests, much will depend on how you set up the folder structure for your Projects to begin with.
I like this structure, as it makes it so easy to migrate, or to Delete, when finished.
D:\ [Project Name] w/ PREL (Project file)
When I gather my Assets, I will Copy those into the appropriate folder, so that the originals are outside the Project folder structure. Everything is in the Project's folder structure. If I need to move these, I move the entire Project structure, and just link to that new location, when I launch PrE and it asks "Where is file _____. AVI?" When I navigate to that one, PrE will then go through that folder, automatically linking to all used Assets. I then repeat for the next folder, and then the next.
When I need to Delete, I will do an Archive of the Project to an external, and then just Delete the Project folder, Deleting all of the sub-folders and the copies of the Assets.
Now, mention was made of the edited Clips. Unless one has done an Export/Share, there are no "edited Clips," just the Clips that were used as source, and then the instructions on how to process those, in XML language in the PREL (Project) file.