Depends on your OS.
If you have a new OS it might not work or might not work flawless.
Installing has to be done always from the original installer or an installer with the same language, version and plattform as your original installer was, when you download it from Adobe's web site (e.g. if your new computer has no CD drive, or the CS is broken). You will always need your serial.
You should always deactivate the old version as you can install it on 2 computer at maximum.
Thank you for answering
do have a CD drive and the Adobe installer is what I am talking about
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Did you enter the serial number?
Yes I entered the serial number and Adobe recognized and said it was a valid number.
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Then it should be all set, but you may need to go to the Help menu to activate.