The C3, which runs about $35 in the 1-gigahertz model, uses the Socket 370 pin arrangement, so it is potentially an upgrade for older computers that use the Pentium III and the original Celeron, even if you aren't worried about noise and power consumption. I say potentially, because there are some compatibility issues. On my first stab at a music server, I dropped a C3 into an old Intel motherboard that had contained a Celeron, only to discover that it wouldn't run a processor faster than 500 megahertz. So if you're planning to upgrade, check the brand of motherboard in your computer and refer to the company's Web site to see whether it supports the C3. In some cases you may be able to download a BIOS upgrade. At that point about all you need to do is swap in the chip and reset dip switches or the BIOS to adjust your speed upward.