Beefing up my PC

Good People,

I've been reading around for a bit trying to glean some answers here and there and thought I'd ask for some advice that I have yet to see specifically addressed. I'm building a video editing PC that I feel is teh best I can do within my budget (it's strictly a hobby) and since I'll be entering grad school soon I thought I'd buy something that would last me a bit since chances are I won't be able to afford anything else for a few years. That said, here is what I'm building from followed by what I'm building to, if that makes sense.

Current build:

Case - Antec Nine Hundred Black Steel ATX Mid Tower
PSU - Antec (I can't remember if it's 750W or 850W and can't see the label)
CPU -Core 2 Quad Q6600 2.4 GHz
Mobo - Asus IPIBL-LAHP/Berkeley-GL8E
Vid Card - EVGA GeForce 8800 GTS
RAM - 8 GB
OS - Vista Premium 64-bit (this is an OEM version)
HDD 1 - Hitachi 400 GB (for the OS & swap files)
HDD 2 - Seagate 640GB (for software & scratch files)
HDD 3 - Seagate 640GB (for video files)


What I'm upgrading to (changes are in bold):

Case - Same
PSU - Same
CPU - i7-930 Bloomfield 2.8GHz
Mobo - EVGA 141-BL-E757-TR LGA 1366
Vid Card -Same
RAM - CORSAIR XMS3 12GB
OS - W7 Premium 64-bit (full retail version)
HDD 1 - Same
HDD 2 - Same
HDD 3 - Same (for source files)
HDD 4 - Western Digital 1TB Black (for output files)

My question comes in the form of asking which steps I should take to ensure the best possible transition. I've got a lot of variables in there and I'm just one step above a complete novice. Since currently running an OEM OS I thought the best steps for me to take were to: 1. Upgrade the OS (clean install); 2. Add the extra HDD; 3. Upgrade the mobo/processor/RAM. But I was strongly encouraged to actually upgrade the mobo/processor/RAM first, then upgrade the OS and finally add the extra HDD.

If I understand correctly, though, the current OS is tied to my mobo/cpu so if I upgrade those first I won't be able to boot into Vista. I suppose I could call Microsoft and tell them my mobo fried, but I'd rather avoid that if possible. So I'm hoping the community here will be able to suggest what they would do in my shoes. As a side note, my fiancee and I are in the middle of wedding prep so my replies will be erratic, but I was hoping to do all this on Sunday the 8th.

TIA



EDIT: I forgot to add that I'm also unsure if I should leave my graphics card unplugged until everything else is settled or plug it in right away. That's a variable I'm unsure of in terms of letting my new mobo get up to speed.

First thing I'd do is switch the board to a Gigabyte GA-X58A-UD3R. It's a little more expensive, but it's more future proof since it has USB 3/SATA III support. Next, switch the HDD for a Samsung Spinpoint F3 1 TB. It's cheaper and faster.

You should definitely upgrade the mobo/CPU/RAM first. If you were to install Windows 7 first, you'd just be wasting time on an installation that won't matter. It's better to install an OS once you've got everything hooked up. It's not like you'll be able to plug the HDD into the new parts and have it work right off the bat.

Here's what you should do in order:

1.) Back up any files on the boot drive. You may want to consider using the new HDD for this purpose, as it will be faster, in which case, you can skip this.

2.) Wipe the HDD that has Vista installed. Completely reformat it.

3.) Install the new board, RAM and CPU. Hook everything up, including the extra HDDs and GPU.

4.) Make sure everything boots up and check BIOS to make sure all the settings are correct, especially the RAM.

5.) Install Windows 7. Make sure to select the correct HDD as the boot drive.

6.) Enter Windows and update all the drivers.

7.) Run some diagnostic tests to make sure everything is working correctly. Check out Step 10 in the "Step-by-Step Guide to Building a PC" (link's found through the sticky at the top of the forum) to see what you should run.

It gives you a clean base to start the installation from. Having two OS installed improperly (and one that's not likely to work) can cause issues.