Can't Download Mathcad 15 to be able to convert older documents to prime
My son bought mathcad Prime for a class. The teacher told him to buy an older version from an older student, that Prime would just cause him problems, but he insisted on having the newest version and it was only $99.
The class uses a lot of older sheets as examples. My son can open none of them, because the converter requires mathcad 15. We have followed every link we can find in the documentation, but every one seems to require either a) a Mathcad 15 product ID, which we do not have or b) some expensive annual technical support account, which we have no desire to buy.
PTC has not yet responded, in part because, again, it seems to require some kind of paid product support even to file a help request. We emailed them, but I guess since we are not paying extra money we may not get an answer. Any help?

