Windows 7 Home Premium won't boot from disk

I just did the reinstall from a USB drive and it worked perfectly! Thanks so much everyone

I had similar problems.
I wanted to do a clean install.

I had two OS installed win7 32bit and 64bit on separate partitions.

I set the Bios as recommended above: make sure DVD Rom is 1st boot device and that 'Allow boot from other devices is set 'Yes'.
Still wouldn't load the Win Install Files from the DVD on Boot-up.
There was this flashing screen as the nVidia Card tried to figure out which mode to use.

Someone suggested load Optimization defaults in Bios, so I did that, also making sure 1st boot device was DVD and boot other devices set to 'yes'.
On Boot-up I got the nice MSI splashscreen and boot-up was quicker but still no load from the installation disk.
Some folks suggested disabling the Vid-Card driver in Windows and then trying to boot-up install.

Although worried that I might lose Video output altogether, from past install experience I knew that the vidcard defaults to 800x600 with no fancy driver installed, which I would have to install anyway on a fresh install - so I was getting ready to do that on my next boot up.

On my next boot-up however, I noticed something I hadn't noticed before.
On the splashscreen it said: Hit TAB to Post.
So I Hit TAB key and the screen started flashing as usual so I hit TAB again, while-the-screen-was-flashing, and PRESTO! the install DVD started loading the files and finally I was at the installation screen. So happy was I, i can tell you.

I repeated the process to see if it was simply the Hit TAB to Post instruction that brought me to the install screen or if it was my freak 2nd hit of the TAB key ,while-the-screen-was-flashing, that was responsible for getting me there.
So I hit the TAB key only once this time and it skipped the install again going straight to Win Login.

So it WAS!! my freako 2nd Hit TAB ,while-the-screen-was-flashing, that got me there - LoL! My 1st Psychic install!
I think the explanation is however, that ,while-the-screen-was-flashing, hitting TAB sets the Vidcard somehow and then it doesn't miss the install, or something like that...

I should also say that after a number of days of frustrated attempts I had a Merciful Encounter with The Lord Jesus' representative, after which this attempt was successful.

Anyways - thought I'd post this as it might help someone.

Aus.

PS: I think I'll make "While-The-Screen-Was-Flashing..." the Title of my first spy thriller.

Welcome to the Forum @Aus7

When you select the ODD to be the first boot option and during POST it finds a boot able CD or DVD it will splash a message:
"Hit any key to boot from CD/DVD" with a count down clock. If you hit any key it will boot from the CD/DVD, otherwise it will boot from the second boot option.
What seems to happen in your computer is that the message during POST ("Hit any key to boot from CD/DVD") was hidden and when you hit ed Tab it began to boot from the CD/DVD