Problem: new notebook ASUS M51Ta was delivered with Windows Vista pre-installed. Customer reqires Windows XP instead.
This is short HOW-TO INSTALL WINDOWS XP on ASUS M51Ta.

Specifications of "my" ASUS M51Ta:
Date of purchase: 12/2008
Link: http://www.alza.cz/asus-m51ta-as028c-d99102.htm
AMD Turion X2 Ultra Dual-Core ZM-82 / 2,2 GHz
Chipset: AMD M780G
15,4" TFT WXGA+ ColorShine, 1440 x 900
ATI Mobility Radeon HD 3650 / 512 MB
2 x 2 GB DDR2 800 MHz
HDD 320 GB, 5400 RPM, Serial ATA
Microsoft Windows Vista Home Premium

Problem #1: BSOD appears instead of installation Windows XP.
Blue screen of death appears after a minute of installation process running in text mode.
(btw whole installation "pre"-process is blue and textual)
Solution: In the BIOS, look for IDE Configuration and set the SATA from "Enhanced (AHCI)" to "Compatible (Natural IDE)"... You'll notice over on the far right hand side of the screen that the help section seems to already know of our problem :)
Link: http://www.eggxpert.com/forums/thread/375716.aspx

By now, you are able to install Windows XP on your ASUS M51Ta.
For dual-boot (Vista and XP) follow this link: http://apcmag.com/how_to_dual_boot_vista_and_xp_with_vista_installed_fir...

Problem #2: Xp Drivers. Absolutelly no support from Asus
Usefull links:
http://www.gtopala.com/
http://www.drivers-xp.com/asus/asus-m51va-windows-xp-drivers-download/
http://www.driverheaven.net/driverheaven-tools-discussion/168794-m51ta-r...
http://www.driverlot.com/asus_m51va_audio_sound_windows_xp_.html
http://www.drivers-xp.com/asus/asus-m51va-windows-xp-drivers-download/
http://www.driverheaven.net/modtool.php

* VGA - only basic mode, drivers from ati cause black screen, no progress...
Even if u disable HD 3650 and allow HD 3200 only.
Even if u choose the correct resolution.
Black screen, no more fun.
Max. resolution with "VGA" driver is 11.. x 8..

* no sound, camera, fingerprint reader...

* cannot find any suitable drivers for AM M780G chipset...

No more progress.

It is possible to use the notebook in this condition for work in an office.
Not for games, not for multimedia.

At this point I decided to show both alternatives to my customer. Vista and XP running on the identical machine. All required programs working under Vista even under XP. Guess what - VISTA IS THE WINNER. Statement of the reasons (why to use Vista instead of XP): better looking icons during log in dialog.

I really "love" those Windows users...
God bless Linux!