How to replace fan
How to replace fan on dv4000 model EW874EA#ABV
The HP Pavilion dv4000 laptop (model number: EC681AV) was released in March 2005. It runs on the Windows XP operating system.
Here is a link to the service manual for your laptop.
Scroll to Sect 5-70 to view the necessary pre-requisites and then the procedure to remove the fan assembly.
The fan assembly is included in the heat sink assembly spare part kit, spare part number 384622-001
Here is a link to suppliers of the spare part. It is not a recommendation to use them, it is shown just to give an idea of the price. There are others online that may suit you better. Just type 384622-001 in the search box to get results.
Hopefully this is of some help.