Citing its so-called 'End User License Agreement' (EULA), Microsoft is cautioning the users against the allurement of going in for a 'clean' installation of the full version of the October 22- released Windows 7 OS by hacking the upgrade version, saying that the procedure is 'illegal.'

With a number of blogs and Web sites explaining the 'hack' of the upgrade disc, for saving at least $80, Microsoft has drawn the attention of the users to the EULA contract that underlines the legal terms and conditions about the what users 'can' and 'cannot' do with any commercial software.

Reproving the OS hacking procedure, Eric Ligman - global partner experience lead for Microsoft's Worldwide Partner Group - noted in a recent blog post: "Over the past several days there have been various posts, etc. across a variety of social media engines stating that some 'hack' … shows that a Windows 7 Upgrade disc can perform a 'clean' installation of Windows 7 on a blank drive from a technical perspective."

Ligman further said: "From the posts I saw, they often forgot to mention a very basic, yet very important piece of information … 'Technically possible' does not always mean legal."

Elaborating about the EULA, a Microsoft spokesperson said that a Windows 7 upgrade on a PC that does not already have a fully-licensed version of an eligible Windows copy, either of XP or Vista, amounts to the violation of the EULA.