I am looking for a shopping cart that once installed inside the server, every domain inside the server can use, save me trouble of installing again. Of course best if free : )

Sounds like you are looking for a PHP system when you say free. There is a small ASP shopping cart from http://www.metalinks.com that is free. You do have to install it everytime into the domains though.

I seen a dll type previously seems to be able to be hosted for all domains, just cant remember the name : ( hope someone out there know it, not free, but I think for a whole server should be worth it.

So not for free anymore? Are you speaking about Miva or something similar?