Windows installation problem

I gave you the flash stick install method in Post #8. You can extract the DVD ISO using ImgBurn.

I'm confused about why you are disabling the 500gb HD in BIOS. You said that even if you set DVD drive to boot first, you get bootmgr is missing error if that HD is not disabled? This error means the HD is attempting to boot, not the DVD.

What is on the 500gb HD? Which HD did you wipe to try install to it? Is it possible you could unplug all but the target HD to see if it solves the problem - disabling might not be enough?

There are nearly a dozen steps given in this thread so please work back through them to try each one, ask any questions if you need to, so we can catch up and continue with the troubleshooting process. We nearly always get the problem solved if all the steps get covered.

Only 4gb stick is required, 8 will do. You can later add tools or files and still keep it bootable as long as you leave the seven Win7 folders it places in the root alone.

According to this article a 4GB flash drive is the minimum requirement for the downloaded ISO, so your 8GB drive will be fine.

Microsoft Store Online

Which worked: flash stick install, unplugging the second HD, or both?

It's OK, few realize the importance of working through the steps without skipping any. Only we who live here often see the skipped step solving the issue later.

Enjoy Win7!