Yep, the logic boards for the eMac and the iMac G4's are quite different. If you so desire to really dig into the inner workings of your eMac, you would be able to remove the hard drive and put it into an iMac G4. HOWEVER, going inside an eMac is not for the faint of heart or for anyone that doesn't have the intention of following CRT discharge procedures. Basically, its a pain in the ass.