I was trying to use the Yahoo Messenger to make PC to Phone calls. Since the Enable Enhanced Security of Sygate 3.0 (Built 520) was used, I could not make PC to Phone calls. However, I could make PC to PC voice chat.

According to Yahoo Messenger help:

ˇ§If your computer is connected to the Internet through a firewall, the firewall will have to be reconfigured to allow TCP connections to vc.yahoo.com ports 5000 and 5001.ˇ¨

How do I open these two ports?

P.S: My PC is Windows98.