Over/Under clock = freeze

i have a laptop, compaq presario 1500 that overheats because they stuck a northwood pentium 4 at 2.4ghz. For a while i tried cpu throttling but it isnt helping my battery power, neither is powerplay w/ my mobility ati. I recently got the winbond thingy that changes the fsb, as i found out the chipset im using is an intel 845mp and the winbond chip i think is W83194BR-B. When i change the fsb in cpucool it just freezes my laptop. i actually have to pull out hte battery on this thing to reboot it. I was wondering if anyone had any suggestions on underclocking this burning pile of doosh.