the originals exe is named "generals (BACKUP)", and the cracked is named "generals". Copy and paste generals into wherever you installed zero hour. The default location is "C:\Program Files\EA Games\Command & Conquer Generals Zero Hour\".
If for any reason you need to revert to the original exe, rename what ever no-cd exe you have to an alternate name and, then copy and paste "generals (BACKUP)" into where you installed zero hour, and rename it to "generals"