P4 2.6 sSpec No SL6S3 temps

hiya i am very new to computer building and am learning slowly about certain things.

ive come a cross a a few things i am worried about. I currently have a P4 2.4 that on idle the temp is around 18 degree's c. my brother has just brought home a PC with a P4 2.66 and with using Hmonitor have temperatures of 42'c is this normal? or is my 2.4 running too cool??

ive been on the intel site which has probably just baffled me even more, but i have 24hr's to tell the company that we bought it from if there is any issues with the pc. im not sure if this is an issue or just its normall running temp..

if someone could advise me on how to go about it, i would be eternally greatful

Well, you really don't have problems with running a pc too cool. However, I doubt that that temp is accurate if you're using air cooling, unless the computer is in a cold room. Is it a 2.4c (northwood core, 800mhz fsb) or one of the older ones?
42 C is high for an idle temp, normal for a load temp, so you'll have to specify. Can you see the temp on either computer in the BIOS?