If you have a valid license key from a purchase in the early 2000s but lost the installation CD, here is the safest approach:
: When prompted for a serial number, use a generic trial key provided by the vendor. For newer versions, keys like 775500001 (v15) or 775600001 (v16) are standard. For version 8.0 specifically, historical sources cite 775250001 as a trial serial number. sigmaplot 8.0 free download