Windows 7: Can't stream video when online

I have just upgraded to windows 7 hp from vista. For some reason I can't stream video such as YouTube. I have deleted and reinstalled flash player a number of times. Please help. My broadband connection is fine and runs at about 3 meg. I have a laptop running xp which is perfectly fine, so there must be a setting wrong somewhere (I've got the same problem with my main mschine which is running vista)

If you upgraded to 7, reinstall 7 completely for a clean install. Then try the first 2 guides in my signature and image 7, just in case something breaks. If you didn't upgrade can you fill in your system specs with the preparation section in my troubleshooting guide.