I have a valid serial number but cannot install Elements onto my new computer and the help staffmember Rahul suggested I contact Forums to discuss it with the 'experts'

So, I bought Elements 7 several years ago and have now purchased a new computer but cannot install it from  a software download (the purchase was a diskette) as I get a red cross mark for a valid serial number?  Though Rahul, after thirty odd minutes, confirmed the serial number was valid he referred me to a community forum for a problem which seems to me to be a business problem?  Though I am happy with Elements as a product this experience has left a bad taste in my mouth about Adobe as a business.  If Adobe thinks this is a good way to get me to buy the latest version of Elements, it isn't.