I agree with compres.
I was going to mention that part but i just had a guy who swears all he did was change the latency from cas3 to 2.5 and smoked (literally) his mobo. I have never seen or heard of a mobo being smoked for that, but i wouldnt want to give out advice that caused this, specially when new here as i am.
I dont think that can really happen but this guy swears up and down, but i have seen cases where these things are said but didnt really happen like that at all.
I know for my part, sometimes i had ram that didnt work at 2.5 but when the ram was taken out or changes done in bios, all was well. Some ram wont allow a change, others will. I think its pretty safe to experiment.
Remember, like google, bios reset is your friend.