Windows Aero Interface: Disable this by right-clicking your desktop, selecting Personalize, and then picking an option under the Basic and High Contrast Themes.

Antivirus software: Just ensure that no active scan will be running while you're live.

Anything that uses Flash: Online videos, games, ads, and so on. (Don't kill your Flash Media Encoder or your ustream window, of course.)

Next, you'll need to tweak a few settings in the programs you're using to do your Webcast. For example, each app you're using has its own video preview--turn all of them off.

If you still see issues, you can assign different processes to different processors--particularly useful if you have a quad-core processor, like a high-end Intel Core i5 or i7. This setting is called --check the above video for a guide to setting this up correctly.