imac not working ....please help

My partner came across a fairly new imac without an internal hd. So ive been trying to help him get it up and going. Installed a seagate sata 1.0 tb, no luck. Read up about the heat sensors and what not. Shorted out the heat sensor, fans ran rapidly, but hd didnt work using osx install discs. So i had an old 24' imac with a 250 gb. seagate laying around (motherboard went bad) that had 10.5.7 leopard installed on it. The 27' imac recognized it when holding down option, but wouldnt boot up from it. install discs would boot up,and give me the options (chose english) waited for it to install, like it said it was doing, then it came up as "osx cannot be installed on this computer" I was able to go to disk utility and repair disk, tried erasing hd, starting fresh, but still nothing. Then i booted up in safemode and it gave me alot of details that were foreign to me. If you havent already noticed, im still sort of a noob....
imac intel core i5
2.8 ghz
5 gb memory
4 cores
If you would like to see the details from the safeboot....can i send a pic? or i will write them out if need be. let me know if you need anything else on this imac...would really like to get this unit up and going. thanks 4 all the help on this post and all the posts i read whenever i struggle..It really is appreciated when some1 takes the time in responding on an issue you just cant conquer on your own...thanks again, The Dirtybird