i have macbook (white) 2GHz core 2 duo, 1 GB Mhz.
Os x version 10.5
since i'm familiar with Microsoft OS i used WINxp SP2 from the moment i've bought it (a year ago).
recently i decide to try what was destined for the macbook- it's original OS x
during the installation everything was well-behaved.

But when i was tweaking (after installation was finished) thru system preferences, it suddenly shut down. since im Os x noob i thought it can be some "Os x procedure".
now almost everytime ,i can't predict when it will shut down, but it surely happens.
i read about the Heat problem, and comments about users who were tend to
replace logic boards, some say it did fix and some say it didn't

i must mention it doesn't happen with Winxp !

pls. help me shed light on this subject , what's wrong with my Os x-macbook relationship ?