My computer freezes when watching videos online. HELP?

I have had my computer for over 2 years and it has been working perfectly well up to now.
Recently the hard drive was replaced from a 250gb to a 500gb, and just last week the screen was replaced.

For the last 4 months whenever I watch videos online my whole computer freezes for about 5 minutes and the sound of the video buzzes.

I have no idea why my computer is doing this and I have tried many ways of solving it to no avail :(

I deleted the content of my temp folder as this is what one blog post said, didnt help. I tried using the microsoft fix it program but no problems were found, and I tried updating my graphics card but it said it was already up to date.

This freezing has been happening on all web browsers; chrome,firefox,IE and Opera.

The only thing that I can think of that may have caused the problem is that about 4 months ago I was fiddling with settings in the program CCleaner, but I cannot remember what I did :/ The rest of my computer works fine!

Does anyone know what may be wrong and how I may fix it?

Thank you :)

Here are my computer specs:

• Packard bell TK37
• 500GB HDD
• 4GB Ram
• Intel Core 2 Duo 1.80Ghz processor
• 64 bit Windows 7
• Mobile intel 4 series express chipset family display adaptor