Can I swap out an Intel Celeron processor for a Pentium 4 as long as they are both socket 478?

Not neccessarily- it depends upon the motherboard... the socket type is a necessary, but not sufficient condition for upgrading. Many motherboards only accept processors up to a certain speed. Some current socket 775 motherboards can take Core 2 Duos but not Core 2 Quads.

Run CPU-Z or SIW to see the exact motherboard model, then check the list of compatible CPUs.

http://www.gtopala.com/

Probably. In addition to socket size, there are power considerations and BIOS support to consider when considering CPU upgrades. If that computer series ever supported Pentiums, then it's very likely that the BIOS will support Pentiums as well.

Information about your computer or motherboard would help nail down compatibility questions.

The thing that you want to look for in a chip is the FSB and the L2 Cache. If the FSB is around 1GHz then you have a quality chip. If the L2 Cache is around around 1GB then you also know you have a quality chip. The faster the FSB runs the faster your CPU can flow information through it, the more L2 Cache the more super fast memory you can store on your chip. These two things really facilitate how fast your processes run. Also the Pentium architecture is far superior to the Celeron.

Use CPU-Z to identify your MB & google it (or visit MB mfr's website) to find out if it supports the CPU in question. Sometimes you may have to upgrade your BIOS to make it compatible. But, it will most likely be so, as long as they're both socket 478 (statistically speaking).