"PTC" is the name of the company. There are no "IM" or "SI" products, it doesn't matter what the (very) old names are.
The name of the product is now "Windchill RV&S", this is what you need to research. However, I tried to find some information about it on PTC's web site so I could give you a link, but I can't find anything. It seems PTC is promoting "Windchill PLM" and trying to hide "RV&S".