I suspect this is a laptop which tends to limit cpu upgrades. If this can be done, you will need the m-version or mobile cpu of that P4 otherwise if this becomes a desktop cpu(it has been done) they were extensively cooled to work. So, even if you could cool it better, i don't see it happening well from what the maker provides. This also may not be a direct unplug cpu and drop-in new cpu arrangement. it maybe one of the "moduled cpu" and thus again has to be a true replacement or if capable resolder new for old. So, overall this isn't as easy as it seems. if you haven't already look at the cpu once torn down or review its repair manual if available. You maybe lucky here as Dell offers that in many cases unlike other makers just the users guide.