It's confusing to read your post and the title of your thread. What's the problem here? When you try to play an Internet video, do you get an error message? If you don't have an anti-virus go to http://www.microsoft.com and download Microsoft Security Essentials. It's free and quite effective. Install it and let it update itself then under the Settings tab, change the scan from Quick to Full and time of that scan to one when the machine will be switched on. Alter the percentage of resources from 50% down to 20% so you won't notice it scanning while you work.
When you've done all that, run the Full Scan to make sure you're fully protected.