If assuming your on a tight budget here and thats the reason for the celeron. In that case I will enlightin you that as a general rule of thumb a REAL P4 a few clock speeds slower than a celeron will generally outperform it. For Instance you would be better off to get a 2.2
GHz Pentium 4 over a 2.4 or 2.6
GHz celeron........the slower P4 will outperform the celeron. Overclocking messes this theory up a bit but it holds true at stock speeds.
Dont worry about the BIOS or the build, fairly straight forward. You have alot of advise and info at your fingertips here, just dont get frazled.