For example, if you are a one-PC network directly connected to your Internet Modem, then you will only have one solution to enable QOS. That one way is typically through your Ethernet Card. Windows XP and Vista provide QOS for Ethernet packet prioritization through your PC network card. However, it is always recommended that you use a NAT-Router between your PC and Internet.
If you have a PC(s) connected to a NAT-Router (or wireless router), you will then want to enable both QOS in the router as well as on the PC Ethernet cards.
By default, Windows XP and Vista should have the QOS Packet Scheduler enabled for your Ethernet card. The Windows QOS Packet Scheduler has default packet prioritization that should typically provide sufficient prioritization for real-time applications, such as VoIP from your soft-phone applications, running on your PC.
To check that QOS Packet Scheduler is installed and enabled on Windows XP, navigate to find your "Local Area Connection Properties" window:
Start-->Control panel--> Network Connections--> Local Area Connection--> Properties
On the Local Area Connection Properties Window, General Tab, you should see "QOS Packet Scheduler" Enabled.
As well, if you are using a Wireless Card to connect your laptop to your Wireless Router, you will want to set the wireless card QOS to Enable, too.
Also, on the wireless card, check its Configuration Settings tab Advanced Settings and make sure WMM is enabled on it (Wireless Multi-Media priority), as well as on the wireless router QOS settings.
While enabling the Windows QOS Packet Scheduler (and WMM on wireless card Configuration settings) may improve your soft-phone VoIP performance, it is only one link in the chain of events in the handling of your VoIP packets as they traverse your local network on route to their final destination over the world wide web.