First you need to tell us what you did and exactly how you did it
I moved some of them from my external harddrive to my iPhoto and most of them got copied there in triplicate.
This sounds like you imported an iPhoto library into your main iPhoto library - di you? Note - you NEVER import one iPhoto library into another one - it does not work and creates a massive mess
If yoou did then did you have any photos you want to keep in the library on the main computer?
If you did then you need to restore your backup of that library from before you imported the library
If you want to merge libraries they only way you can is with the paid version of iPhoto Library Manager - http://www.fatcatsoftware.com/iplm/ -
A new computer will have no effect on the issue - going back to before you made the error is the only way to totally recover -- short of that you need to us IPLM to find and remove duplicates and manually finish up what is not automatically found - and this is only a half way measure since you lose all edits, etc form the old library
LN