I'm working on a PC right now that I built for my employer last April. It's got a Prescott 3.2Ghz with stock cooling & a thermal pad. It's been running 24/7 for almost a year now. (Only the occasional restart or if I open it to clean out dusk.)
The office climate is around 72 - 74F all day all night. Now if I were to raise the office temp to say, "90 - 100F" i'm the temps would obviously go up, yet the temp would still be lower then the prescott, even at idle. You just need good airflow - which promotes heat dissipation.
Nubius also made a good point. CPU's have a MAX temp then they throttle or just shut off. Nothing will start on fire or melt.
Don't base your CPU purchase on TEMPS. Base it on what you plan on using it for. For more information about what CPU's are best for what... Just use the search feature of this forum.
