Thanks gibberish, I really appreciate being called an amateur.
cipi,
The point that should be made is that frames are very hard to do right. If you don't know how to make them work right, it is better to do without. Frames are very easy to break and that's when they make your site look crappy. Either way, splitting different parts of X-Cart into different frames will get fairly complicated.
I put my cart into a frame on my existing site and it works great so far. I haven't tried to break it yet, so I'm sure I'll have some changes to make once I start testing. I didn't try splitting out different parts of the cart into different frames, so it may not be what you're looking for. You can see what I'm working on at:
http://www.amarillobolt.com/abc_cartindex.html
Hope this helps in some way.