you mean format the HDD 1st before installing it on a mac?

i would say just go ahead, i just did that a week ago and nothing is happened to me(touch wood) and they are working great.
but i havent update the firmware to 1.7 as lots of users make complaint on crashes and their machine slow after they have upgraded the firmware.
of course there are lucky guys anywhere.........just dont dare to take the risk.

this 1
EFI 1.7

i tot that was only designed for mid 2009 model 13"uMBP and 15"uMBP?

yeap, you have to install the os again. if you have set up the time machine on an external HDD, you can just transfer all your previous files to your new HDD by just a single click. to install os on a new HDD, simply insert ur os x CD and follow the on screen instruction. very simply.
im a newbie too.....hope it helps

some programs did raise up the heat problem on macbook pro.
some like
msn messenger
facebook games
adobe suite
youtube and some flash website.

a silly question here,
i've been using my mac for almost 4 months and i just realized that the firewall is not on and i didnt kena any Virus so far..."touch wood"? was it purely my luck or my machine will finally get worms if i keep my firewall remain off? imaging if im using my PC, Firewall is a must but not sure about Mac?
anyway, i have just turned it on..just need to find out is it very important to turn it on or off?