Heavy CPU usage and fan noise

[MG2R]

I'm writing this from my Dell Vostro 3350. A 13" core i5 laptop that used to have Windows 7 pro installed. While using Windows the cooling fan would almost never come on during normal browsing (firefox) with about 5-10 applications like Thunderbird, Office, Putty, Skype, etc running in the background.

Now, II have Ubuntu 12.04 installed on this machine, because I used to love Ubuntu (haven't really used in about two-three years due to needing software like Autocad and the likes). Now, the cooling fan is almost constantly on while doing almost nothing at all. I can see my CPU frequency boosted to the max a lot of the time.

For example: when I watch a YouTube video in full screen, it uses an extraordinary amount of CPU power so the fan needs to work it's *** of to keep my laptop at a comfortable temperature.

Since when is Ubuntu this CPU-heavy? It didn't use to be like this, if my memory serves me correct. Is there anything I can do to help things? I hate fan noise, so the situation as it is right now is quite unacceptable for me...

Thanks to anyone who replies.

[mikewhatever]

...and what's the process that uses the CPU exsessively, "when doing almost nothing"? Note, whatching youtube videos does not qualify as "almost nothing", as flash is know to be a resource hog on Linux.

[MG2R]

Mainly Firefox and its plugin-container (flash) and Thundirbird are driving the usage up. At the moment I only have Skype and two terminals idling in the background.

Also, X is always at top, which seems logical.

When I say 'doing almost nothing', I mean doing the same stuff that didn't use my CPU enough to trigger the fan on Windows.
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[mikewhatever]

Not sure I can add much to the above, Flash on Linux means heavy CPU usage. There isn't anything anyone can do about it. Try taking it out of the equation, and see what happens.