In reply to iksander:
Are you looking for a brand of window system like Rehau who make the parts that are assembled into frames or a company that makes and or fits windows.
If it's a the former, pretty much every company will have a range of products for various applications and prices. If it's the latter then we need to know where you live.
The bigger the windows the smaller and less significant the frames look so it's less of an issue.