Search function don't work when I press Enter key.

I have a strange problem with Internet Explorer.
In some web sites, when I write a thing in search bar and click Enter on my keyboard, nothing happen. I have to press the "search" button on the site.

For example, if in YouTube I write "anything" in search bar and then press Enter, nothing happen. I have to click with mouse arrow on the "search" button.
This happen also in other websites.
I have Vista Home Premium 64 bit. It's all updated, also Internet Explorer.
Before the format of my HD that I made 2 days ago, all work fine.
SORRY FOR MY ENGLISH.

Does the enter button still work, when you are typing something and want to go to another line below? If your enter key doesnt work with anything, then its keyboard fault. If your keyboard doesnt press enter only with the search boxes, try to use the seach with neter in another browser (safari, firefoxor opera), to try to trouble shoot.