Making a Quake3 backup!

I rently bought a new computer which came witha burner. I have now decided to make backups of all my games. The first one I tried was Quake 3 and all the files copied but when I got to run the game this message comes up :

D:\Q3Arena\quake3.exe is not a valid Win32 application.

Could somebody please tell me how to copy this successfully