New rig will not boot

I've completed a new rig today, but it does not boot-up. I'm guessing the problem is with the HDD which I took from another rig. With so little info would anyone hazard a guess as to whether the HDD which has Vista on it is the likely culprit?

The new mobo is a gigabyte and the old mobo was an Asus.

PS: I did not delete the data on the HDD before removing it from the old rig and since I gave it away there is no way to reformat if indeed the HDD is the source of my problem.

 

are you getting a power light on the cpu? are you getting any display on the monitor? does the monitor light just blink with a black screen?

 

I can't even guess at what that means.

Answers to abz1nthe questions would be required to even "hazard a guess".

Does the machine post? Does it start to boot Vista and fail? Does it do anything, fans come on. HD spins up, make any sounds or beeps?

 

Microsoft OS' puts signatures on about 10 -12 location when installed on a new HDD installation. They tag the Motherboard, CPU, Memory & HDD in several location. that how it knows when you change memory or any other component. If this new PC build has too many changes in components, then most likely it doesn't recognize the compatability of this Windows to the System it's try to open.

So if you are not getting any POST screen action, you might have to reformat, and reinstall OS, so it can recognize the PC.

I work at this for a living and only once did I make MB, CPU & Ram changes that the HDD actually worked without having to reinstall OS.

You said about reformating without the computer. If you have one of those USB to SATA/IDE Cables, you can go to the library and use their PC to reformat it their, takes 5 - 10 minutes to do.

In case you don't know, After you plug in HDD using this system, Right Click on My Computer, Click on Manage, Clcik on Disk Management, find the drive in question, Right Click and Format

 

This is kinda old (vista), but, I'm sure it is the same with win7:

site: http://www.microsoft.com/uk/windows/products/windowsvista/buyorupgrade/activationfaq.mspx

 

Sorry guys, I was working and therefore unable to read your replies until today.
The update is, I removed all hardware and re-installed everything, now I'm posting on the new rig. :-D

Thanks for all the input.