I purchased my computer direct from a manufacturer, it came with the instruction that it did not include a recovery or Windows disk but had been loaded with a new system recovery procedure, pressing F10 when the system boots leads to the option of a destructive or non destructive choice, but as they have now gone out of buiseness I took it for repair to a local shop. They fitted a new motherboard & installed a pirate copy of Windows XP Pro.
Can I upgrade from my present state to Vista without first paying for a Gen Windows validation ?

Have you paid for that copy of windows xp? If you did and found out later that it was pirated, go back to the shop where you changed the mobo and ask for a refund or a genuine copy of windows xp. Don't think you can upgrade from a pirated version of xp to a licensed version of vista as it may check the xp install key (as sp2 of xp does).

Your key should be on your pc somewhere, usually the side or back.

Can I upgrade from my present state to Vista without first paying for a Gen Windows validation ?

You can't.

But...what you can do is go thru MS's amnesty program, explain it to them, pay a reduced cost for a XP license, and then upgrade to Vista.

Spooky is correct - you can go through the Microsoft program (links to the program appear after you fail validation on Windows Update, for reference), or you can purchase a new copy of Windows XP from a retailer, install it, and upgrade. However, I'd suggest reporting the vendor who wiped your disk and installed an unlicensed copy of XP, and they should be providing you a licensed copy at this point.

Is there anything stopping you from simply storing all your important documents etc. on an external hdd or sending them to yourself on hotmail and simply performing a fresh install of vista? The only reason I ask is because I'm in a similiar postition and that is what I plan on doing.

I think he wants to upgrade. That generally costs less.

Yes I did a upgrade to Vista from a less then legal XP with no problems.

well of course you did, and of course you can. But his issue is that he got screwed by the place that put in his new MB and installed a pirated copy of XP for him, and I assume that he didn't know about it until after it happened, and now he seems to want to do it the right way.

Eventually, no matter what hacks and cracks are out there, MS is going to kill any pirated copies. Heck, all they have to do is put any killer code in any update what so ever for any MS product, or even in products from any of their software partners. Remeber the root kit thing from Sony a little while back? People didn't know about that for a long time, think about how easy it would be for MS to introduce some code in a game from a MS partner somewhere. Or how about the media guide in Windows Media Center (WMC) that will download when your connected unless you specifically tell it not to in the media center settings? Or how about that privacy thing in WMC that you have to check to use the guide but also sends information to MS also? A lot of people don't realize that the default search in Vista is thru MS, and they send information to you each time you use it. How about the phishing filter in IE, all they have to do is turn on a validation check when the phishing filter does its thing and they can kill your OS that way.

Its only a matter of time, and if they can't get them all this time they will learn from their ways and know more for the next version of windows.