firefox cpu goes insanely high when stream video

[merrygoround]

so like i had this problem for a long time already T_T, i really want help!

each time i stream a video online, i watch for 5 mins and all of a sudden the back of my pc makes a very loud vrrrooom sound. so i check the task manager and i notice that the firefox cpu is like 70-89%. when i stop the video, the cpu goes down and the sound from the back of the pc stops. i installed the latest flash player and plugin already but its still like that. its so weird! help

i have windows XP
media center ed.
version 2002
serivce pack 2
pentium 4 cpu
512 ram

[Broni]

What processor do you have?

Add another 512MB or RAM, and things will get better.

[merrygoround]

woo, i dont know how i can do that. is that the only way?

[Broni]

Upgrading RAM?
Trust me, you can do it.

[merrygoround]

dude i dont even know how a RAM look like, and installing it? you're probably a computer genius

[Broni]

I'm not, but if you're brave enough, we can guide you through.
Do you have any friend/family member, who could help a little?