InDesign CS6 (not the current version) can try to read PageMaker files, sometimes it works. But anyway, what is the exact error message you get (don't tell us your serial number!) I hope you are installing on a compatible system - Windows XP or older.
It says it is not an Adobe serial number and it's the one on the package. This morning I found findserialnumber.net that had a list of serial numbers and one of those worked. weird. I had heard that older versions of indesign might read it but I didn't want to purchase that program just to read one file. thanks