Why don't you swap the Windows 7 HD into Disk0 and set it first to boot in BIOS setup to see what changes?
Is it possible you disconnected or dislodged the video card when you cleaned out your PC? Look in Device Manager to see if your video card is installed, working and has the latest driver
from optional Windows Updates.
You did guard against static discharge and used canned air and not a vacuum attachment, correct?
If you reinstall plug Windows 7 target HD into DISK0 and unplug all others, follow the steps to get a perfect Clean Reinstall - Factory OEM Windows 7
which are the same for retail.
In my last post I also gave you three other things to try which you did not respond to. Solving these problems requires utter thoroughness with no steps being missed. If you have questions, just ask back.