Windows 7: Using same key to install on two computers

Simple question, is it possible? My sister's laptop is running the RC that I was using recently. But I upgraded, using the key I bought for the Windows 7 Retail from the digital river student sale offer.

Her computer will also start to expire soon, so I need to do the same there. But this is the only key I have, and I used it on my computer. Is it possible to use the same key on her laptop as well? I know probably not, but I thought so about being able to upgrade from RC to RTM too, except that was possible, so you never know.
Thanks.

No, that would be illegal. You need a separate key for each installation.

In addition to being illegal and not moral, Microsoft is beginning a crack down on all who do not have legally licensed OS. You can get an upgrade DVD for a little more than about $100. The few dollars spent would be the best way to go.

Worth the price as well...

Aside from being a violation of the license agreement, the activation will fail on the second system.

There are always ways to get around that, but it'd be best to get another license.

Yeah, thought so. It is easily worth 100 dollars of course, but I dont know if my sister will be able to afford that right now.
I guess we'll have to figure something out.

If Windows 7 is already activated an one PC and its is installed on another PC (with same Prod key) even when activated at time of install, what happens?

Is this even possible or is the activation checked later in the second install and, when it is, what happens then?

Welcome

It is against Forum Policy to explain how it can happen, but trust me it can.
If a person is caught, worse case scenario, MS can pursue criminal charges; its theft of service. Best case scenario, you lose one of the OS. It will be turned off.

You can get a 32bit Windows 7 for $89.99 here. You have to use this promo code: EMCYRYZ54. Without the promo code and for the 64bit version it is $99.99.

By the way you can use the same key to activate either the 64 or 32 bit versions.