Yes, you can try a keyless Installation of Windows 7. But be sure that you enter the product key to activate Windows wihtin 30 days grace period. Once the grace period of 30 days end your system will go in no boot and you may have to reinstall the copy again.
Unlike Windows Vista if you purchase Windows 7 DVD you will get Edition specified Disc and at the time of Installation you won't get an option to select the Edition. Almost at the last stage of the Installation you will get the option to enter the Product key
which you can skip and try to enter the Product Key at the time of Activation.