If you need guide to install Windows XP in this model refer guide here and here is your stat drivers:
GUIDE TO INSTALL XP

ICH9 sata driver,
Download (microsoft)
Download (mediafire)

if you have any problems leave your comments. details of the specification is at the end of the post.

INTEL CHIPSET:
Compaq Presario CQ40-647TU
INF Update Utility - Primarily for Intel® 5, 4, 3, 900 Series Chipsets
Download (direct link)
Download (intel website)
Download(mediafire)

Intel matrix storage manager:
Compaq Presario CQ40-647TU
Download (intel site)
Download (mediafire)


GRAPHIC
if you have intel graphic Compaq Presario CQ40-647TU:
Mobile Intel 4 Series Express Chipset Family Graphics Driver (32-bit)
Download (mediafire)

If you have Nvidia graphic Compaq Presario CQ40-647TU:
NVIDIA GeForce G 103M/ G 105M Graphics Driver (186.81 WHQL XP 32-bit)
Download

if resulting in eror use modded driver below:
Download
3-step process to install:
1. Download driver, double click and select extract,
2. Download modded INF and replace original INF in extracted folder,
3. Install & reboot.

AUDIO:
Install MS-UAA first:
both ms-uaa sp33867 and kb888111 are similar files.
Windows XP SP2: Download (SP33867.exe)
Download (KB888111)
Windows XP SP3: Download (KB835221)

Then restart, and install AUDIO Drivers:

IDT - High Definition Audio Codecs (SP39671)
Download (ftp)
Download (mediafire)
===========================
or try this drivers reported work in xp
SP41500 Download (ftp)
Download (mediaifre)

SP41616 Download(ftp)
Download (mediaifre)
---------------------
First install your audio.
Installing the Audio normally resulting in error, ignore it and proceed by manually install the drivers, read the guide here;
Manually install Audio Drivers.

WIRELESS Compaq Presario CQ40-647TU:
Choose one of the wireless driver base on your specs, if you dont know, just try each driver (there are no risk and will not harm your system)
---------------------------------------------------------
Broadcom: Download

Intel: Download
(requires windows installer 3.0 installed first)
=================

HP Integrated Module with Bluetooth Wireless Technology
Download

HP Wireless Assitant:
Download

CARD READER Compaq Presario CQ40-647TU
JMB38X Card Reader Host Controller
Download

ALPS Touchpad Compaq Presario CQ40-647TU
Download

Synaptics Touchpad Compaq Presario CQ40-647TU
Download
Download

WEBCAM Compaq Presario CQ40-647TU
Cyberlink youcam software 2.0
Download

LIGHTSCRIBE: Compaq Presario CQ40-647TU
Lightscribe system software
Download