You need to provide more information. What wallet are/were you using (Bitcoin-Qt, Electrum, MultiBit)? What operating system are you using (Windows, Apple OSX, *nix)? Do you have additional backups of your wallet, or only the one you made just before the restore? What exactly did you copy and paste?
Assuming that you are using Bitcoin-Qt on a Windows computer:
Did you copy all the data from C:\Users\username\AppData\Roaming\Bitcoin ? That is the location your wallet is stored in.
Exactly. You needed to store a copy of the wallet.dat file. If you have the wallet.dat file from before you restored your computer, you should be able to recover your bitcoins. If you don't have a copy of that file, then you can pretty much assume that you will never be able to regain control of the bitcoins.
