Windows 7 upgrade version without previous OS

[Judgeneo]

A mate of mine said he bought and downloaded the upgrade version of windows home professional 64bit using the student offer on at the time for £35 (now £45 so still cheaper).
He used this to get the OS on the new machine he built by apparently installing it as a trial version without entering the serial, and then updating the trail version using the serial he downloaded, he hasn't had any problems with it at all.

Bearing in mind this was towards the start of the year, I'm sceptical as to whether this will still work or not.
Does anyone have any experience/ideas with regards to if it will work or not. Also how legal is this process :s.

Could save be a lot of money so its certainly worth looking into

 

[Judgeneo]

To qualify for an Upgrade license of Windows 7, the system you're looking to install Windows 7 on needs to already be licensed to a legitimate copy of either Windows XP or Windows Vista and thus, your friend does not qualify for such a license. If he does install it on a brand new system, he will not be correctly licensed. Your friend really needs to purchase either an OEM or a Retail license of Windows 7.

How much is XP these days?

 

[Judgeneo]

Cheers for the advise people, looks like its back to the plan of buying 7 retail