For a long time for downloading files I use Flashget. Very convenient and simple program. By default, the given program does not allow to download more than 8 files Simultaneous.

This number can be increased by the tweak below:

1. Run Regedit.
2. Navigate to [HKEY_CURRENT_USER\Software\JetCar\JetCar\General\]
3. Right Click -> Add String Value.
4. Name as MaxSimJobs -> Set the value as what ever number you want.

After a restart you should be able to download with more file splits.