This si very helpful method if you are trying to download from any site which has time limitation for particular ip.
Here's how to do it in windows:
1. Click Start
2. Click run
3. In the run box type cmd.exe and click OK
4. When the command prompt opens
type the following. ENTER after each
5. Erase your cookies in whatever browser you are using.
Frequently you will be assigned a new IP address when this happens.
Sometime you will, sometimes you will not. If you are on a fixed IP address, this method will not work. If this works for you, you may want to save the above commands into a batch file, and just run it when you need it.