Mac Pro wont work after downgrade

I basically downgraded my mac to snow lepored because i was on 10.7 and when i updated it restarted and wouldnt boot up the disk so i made a new disk and was able to transfer content but when i transfer my apps safari minecraft and other apps wont open also lots of the apps are 10.7 apps and when i try to reinstall osx 10.7 it just goes to this screen http://www.google.co.uk/imgres?q=wont+boot+of+disk+mac&um=1&hl=en&client=firefox -a&sa=N&tbo=d&rls=org.mozilla:en-US:official&biw=994&bih=901&tbm=isch&tbnid=d9UU HSoMAJ5IWM:&imgrefurl=http://forums.creativecow.net/thread/71/862746&docid=i04au gVgQfzUaM&imgurl=http://i1.creativecow.net/u/174622/img_0006.jpg&w=960&h=720&ei= czatUIWRA4LB0QWw4YDgCA&zoom=1&iact=hc&vpx=696&vpy=484&dur=1440&hovh=194&hovw=259 &tx=176&ty=110&sig=109131521132923127409&page=2&tbnh=127&tbnw=166&start=25&ndsp= 30&ved=1t:429,r:43,s:0,i:220