with the 1800+ xp chip you have there will be pits/gaps between the L1 bridges, some
i unlocked only one before, filled in the gaps with clear nail polish, then used rear window defogger repair kit conductive liquid to bridge the L1's together.
look around net / cpu section for more info and tips before you try this.
try setting you ram fsb to 166 and relax all the timings for the memory in bios (i.e. all memory enhancing stuff off, normal timing, CAS3, etc...) and put divider at 1/5. see if it boots and runs there. you can always try enabling the memory enhancements after that.
increasing vdimm voltage may help
increasing the overclock on the cpu will slightly increase temps. if you increase the vcore however, that will increase temps much more.