FrankM,
Downloads for Easy Media Creator 9 came in many flavors, but all those I saw started with RoxioEMCSuite. . . or RoxioEMCDLX. . . as .exe files, or easy_media_Creator_9_ . . . as a ZIP file. From memory, downloads usually had two files - one labelled as the 'program' and the other as 'content'
Downloads cost companies money, and Sonic/Roxio have their downloads handled by Digital River. Your responsibility is to backup your downloaded software, and Digital River won't let you have extra downloads unless you have paid extra for the privilege. Apart from that, Creator 9 is "out of support" now so they probably don't have it any more. I don't think you'll be able to get a download now, let alone a free one.

You won't be able to reinstall version 5 under Vista. Vista doesn't support that old version.
There's one possibility which might help you. There are two versions of a PxEngine upgrader available for download. The older version seems to do a reinstall of the PX Engine, whereas the newer one just upgrades some of the files used. Since you're having trouble with PX.DLL, running the first upgrader and this reinstalling the PX Engine
might do the trick for you. There can be no guarantees, but it's worth a try.
The first upgrader can be downloaded
HERE.If that doesn't work for you, I think your options are
[1]find your download file and reinstall
[2]get another copy of EMC 9 second-hand from eBay or Amazon or similar places
[3]buy some more recent software
Please let us know if reinstalling the PX engine fixes the problem. I wish you well.