Compaq Presario CQ40-337TU Windows XP Drivers

Intel Matrix Storage Manager (Install and Reboot) :
Download

Chipset Driver :
Intel Chipset

Download - Mirror (Direct)
Download - Mirror (Intel)
Download - Mirror (Mediafire)

Wireless Driver :

Broadcom
Download

dotNetFramework 2.0 :
Download

HP Quick Launch Buttons :
Download

Audio Driver :
Install MS-UAA then reboot.
SP33867
Download

Then Install :
High-Definition Audio (HDA) Modem Installer and Driver :
Download - Mirror (Alternative 1)
Download - Mirror (Alternative 2)

Next, Install :
IDT High-Definition Audio CODEC Driver
SP39671
Download - Mirror (FTP)
Download - Mirror (HP)
Download - Mirror (Mediafire)
Download - Mirror (Ziddu)
If installing IDT end up in error, follow the step below :

Installing Audio Driver in Windows XP (Compaq Laptop after Downgrade to Windows XP)

VGA Driver :
Mobile Intel 45 Express Chipset Family Graphics Driver
Intel graphic accelerator 4500MHD
Download

Modem Driver : 

LSI High-Definition Audio (HDA) Modem
Download

Touchpad Driver :
ALPS
Download

LAN / Ethernet Driver :
Realtek 8102E LAN
Download

Card Reader Driver :
JMB38X Card Reader Host Controller Driver
Download

Cyberlink YouCam Software :
Download

7 Unknown Devices
Download - Mirror (Direct)
Download - Mirror (Mediafire)

To install driver for the 7 unknown device : 

1) Go to Device Manager(Windows Button + R) then type "devmgmt.msc", 

2) Right Click on the Unknown Device > Update Driver > No to connect > Choose install from a list or

    specific location > Don't search > Have Disk > Browse to the location of machine.inf. 

3) Repeat step 2 for the rest of Unknown Devices 

Credits : 

Black-x for the link uploaded and the method suggested!