Compaq Presario A900 Windows XP Driver 

 CHIPSET

Download (HP driver)
Download (Intel Driver)

GRAPHIC:
Mobile Intel 965 Express Chipset Family Video/Graphics Driver
Download

AUDIO :
UAA drivers (Must be installed before installing the audio driver):
Download
Windows XP SP3: Download (KB835221)

Install MS_UAA and Restart!
MS-UAA: (if you laready installed MS-UAA above no need to install again, if you do install it again dun worry about that.
Download (sp33867) size 53MB

Then install
Conextant High Definition audio
Download

If the AUDIO still didn’t work read instruction at the end of the post.

MODEM:
(if the modem installed along with the audio no need for this driver)
Conexant HDAUDIO Soft Data Fax Modem with SmartCP Driver
Download

WIRELESS:
There are 3 applicable wireless, choose base on your specs, If you do not know which to choose, try which work for you.

Intel(R) PRO/Wireless 3945ABG Network Driver
Download

Broadcom Wireless Driver
Download

Atheros AR5007 802.11b/g Wireless LAN Driver
Download

LAN/ETHERNET:
Realtek RTL8139/810x Family Fast Ethernet NIC Driver
Download

STORAGE:
Intel Matrix Storage Manager
Download

LIGHTSCRIBE
Lighscribe host system Software
Download

WEBCAM
Cyberlink Youcam Driver
Download

TOUCHPAD
ALPS Touchpad Pointing Device Driver
 Download

CARD READER
Ricoh 5 in 1 card reader driver
Download

HP Quickplay
Download