Internet Explorer 7 allows a maximum of two simultaneous downloads which might be enough for casual downloaders but is definitely not enough for users who download a lot in a short time. I’m on a very fast connection and have no problem to download 8-10 files at a time.

You will have to edit some registry keys as an administrator to change the number of downloads in Internet Explorer 7. To do so press Windows + R, type regedit and hit enter. Navigate to the key HKEY_CURRENT_USER \Software \Microsoft \Windows \CurrentVersion \Internet Settings and create a new 32 bit Dword MaxConnectionsPer1_0Server. Now change that value to a value that is greater than 2.

A second key needs to be created. So, create a new 32 bit Dword and name it MaxConnectionsPerServer. You should assign the same value that you have selected for the key before and assign that number to this key as well.

source: vistawired