How do you replace a Vista motherboard?

Ok, here is my situation;

I have a Desktop PC with Windows Vista Home Premium 32 bit, the whole PC was bought together (it wasn't built at home), so I think it will have an OEM copy of Vista. I want to upgrade the motherboard and CPU on it, but not sure how to do it.
here is the PC:

http://support.packardbell.com/uk/ [...] 101&g=1400

and here is the Mobo and CPU bundle I want to upgrade to:

http://www.tigerdirect.com/applica [...] u=B69-3101

I know how to unplug all the stuff inside the computer and physically replace the motherboard, but I read somewhere that its more difficult than that, like you have to get a new license or something if your vista is OEM. What do i need to do first of all, do i need to create a backup, if so, what program do I use. Do I need to purchase Vista in one of those fancy boxes with curved sides, if so, could you give a link to the right one? Do i have to re-install windows, how and when - before installing the new mobo or after? And do you have to phone up MS?
Please provide simple but detailed instructions because i'm pretty clueless about how to do it.
Thanks very much!

I hate to say this, and don't take it personally, but after reading your delimma, you should just go buy a new HP, Dell, Gateway or what ever. I do not thing changing motherboards and processors, reinstalling OS's is quite what you are up to yet.

OR, you need to enlist the help of a friend who is a little more savy, and has maybe done a couple of builds. At least someone right there with you to confide in and help you along as you do the build. If you are going to do what you say, yes you will need a new OS. I would also suggest you buy a new case, and just move things like your hard drives, and CD/DVD drives, whatever over into the new case.
I would never suggest trying to change a motherboard in a prebuild unless it was a very high end prebuild to start with, and was built with higher end interchangeable parts. Most of the standard HPs, Dells, etc. will be built with elcheapo stuff, causes major headaches when you try to do major upgrades....things simply refuse to fit!

I started to write down your options, and the procedure is far too complex with too much risk for me to explain via posts to someone with your apparent knowledge.

I agree with Shadow. Along with your new mobo and cpu get new memory if you need to, then re-use the other parts, and buy a copy of Vista OEM (with free upgrade to Win 7) from a local vendor. Note that you may need to replace the case and power supply if these have any proprietary connectors.

Thanks for all the answers. I forgot to mention that I have already upgraded the PSU to a 650w Thermaltake, the RAM to 2 GB, and the GPU to an 8800 GTS 640. I have decided to go with a diffrent CPU (the Phenom II x3 720 Black Edition), as I have read reviews that its a good CPU at a good price. I'm on a low budget as well. The Mothercoard that I decided to go with is an ASROCK SKT-AM2 N68-S S (http://www.ksn-online.co.uk/product_info.php?products_id=6697 ). Will these two components be a good upgrade?

and make SURE it includes the Windows 7 upgrade.
(just restating that, Vista is the new Windows ME, sell your grandmother if you have to, you want 7)

wtf dude this is like months old..