|There's a limit, but it's not in the number of windows you can open. The limit is in the maximum number of connections you can have open.|
The following page will describe how to increase this number:
That said, I feel like I'm telling you how to drive somewhere by using only left-turns.
Why are you opening up so many windows? If you want to browse multiple sites or pages, just use a more up-to-date browser that'll let you use tabs. Use almost any browser except Internet Explorer, and you'll find your browsing experience to be much more pleasant. Just download something like Firefox or Opera and start making some right-turns too.