Windows 7 professional upgrade license/instance questions

I installed windows 7 professional upgrade  on my laptop and it's working fine.
I have another pc at home and would like to upgrade this from home premium to professional also.
What are the ramifications of using the same product key?
Sometimes I have my laptop and desktop powered on at the same time at home in the same network.  Any problems with this scenario?
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You are only allowed to use the key for one PC. If you want to use it on another, and it isn't an OEM license, you must first remove the OS from the PC it is currently installed on, and then you can use it on another PC. If it is an OEM license, you can't move it from one PC to another, unless you live in the EU or Switzerland, but you'll have to call m$ licensing to get it activated.

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Robin CMSenior Security and Infrastructure EngineerCommented:
The ramifications are that eventually one (potentially both) of the machines will fail to renew its activation and will end up in reduced functionality mode. So don't do it.
You can still buy a Windows 7 licence for cheap (and get a free upgrade to Windows 10 in the first year), so just do this.
If you have Windows 8 Pro and want to downgrade that to Win 7 Pro you can do that by using an existing Win 7 key on multiple PC's. I have used the same key dozens of times and there are no negatives. Microsoft allow this.

I suspect what the OP wants to do will work but it may not be legal.
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brothertruffle880Author Commented:
Okay.  QUESTION:  What do I purchase?
I have a desktop with Windows 7 64 bit home and want to upgrade to professional.
I have a CD with Win 7 64 bit upgrade files and successfully installed it on on my laptop.  I had a legitimate license which I installed.
Where do I purchase a license for win7 pro 64 bit upgrade.  Since I already have the CD.
Robin CMSenior Security and Infrastructure EngineerCommented:
You should be able to find a supplier that sells unused Windows 7 Pro 64-bit licence stickers. These have the licence code printed on them and are what you'd see on a commercially bought PC. In the UK you can get them for about £40.
Otherwise you'll have to buy a shrinkwrapped OEM edition which will probably cost more and include media that you don't need.
Google is your friend.
First look at the PC shops in your town or close to where you live and buy a boxed version of Windows 7 Pro there. Even if you don't need the files it is still better if you have the DVD. Buying that way you'll be more likely to get a legitimate version of the OS, than when you get it online.

Otherwise you can risk using a portal like ebay, but  you can never really be sure you'll get a legitimate version over a pirated version of the OS that way.
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