IIS7 Page Load Delay

[fr600]

I've recently introduced a new section to download files from my server. The problem I'm having is that whenever I try to visit a website on my server while someone is downloading something, the page keeps loading and don't show up. I've no idea what's causing this. Could you please tell me how to fix it?

Here are some more info:

When someone download from my server at 200-300 KB/s, no one else can browse the website.

I've got 10 mbps, that's like 1.25 MB/s, so 300 KB/s shouldn't be a problem.

Whenever the person who is downloading stops downloading, the site starts to work again.

Can anyone help me with this? Please...