Thanks pSouper

The languages is swedish

No I haven't yet integrated osCommerce with phpWCMS but I will try to do so.
I guess it's easy to use I-frame if you only want to have osCommerce integrated in phpWCMS, the user will have the shop in the CMS but the admin part for you will be stand alone as normal and not in the phpWCMS.
You can take away the header from osCommerce and keep the line for breadcrumb and it will look good I guess. It will look like the shop at ABM Telecom that I made and they wanted to have osCommerce in a frame.
http://www.abmtelecom.com/webshop.html
Their shop is on a subdomain
http://shop.abmtelecom.com but of course the shop on the subdomain is not for the users.
But if you integrate osCommerce in phpWCMS you will not have the topframe and bottomframe like that, the shop will be between the header and footer of phpWCMS so the shop will scroll with phpWCMS.
I will tell you how it goes when I got the time to work on that.