I have a slightly noisy fan for about 15 secs at start up if the PC has been off for a day or so. Started about a month ago. I have removed the other fans and squirted with a trace of WD40, but I am now sure it is the CPU fan. Can this be removed and replaced easily or does it have the 'grease' between it and the mobo. Just like to 'treat' it in case it gets worse. It runs silently after the start up period and speeds and temps are all OK. Asus P4P800-X MB and Pentium 2.4. Thanks.
All the CPU fans I have seen are screwed onto the heatsink and are easily replaced. By grease I presume you mean thermal compound, this is only between the heatsink and the processor, as long as you don't have to remove the heatsink you will not have to remove and replace the compound. The fan should just screw off.