For systems released prior to the release of Vista with SP1:
Vaio/ Any Notebook users if you have the
hidden WAU folder in C:\Windows\sonysys or the directory C:\WAUUPGRD (thanks to terrorbite), you can do a clean install of vista.
Steps to check if your laptop is pre-configured for an upgrade (the presence of WAU contents)
1. Click start and then enter "windows anytime upgrade"
2. Go to windows anytime upgrade and then select the "upgrade to option".
3. Now in the "then upgrade option" it will be clearly stated whether your computer is pre-configured for an upgrade by the manufacturer. If it says so, then you can burn your own Vista install dvd using the method given below.
The above steps do not apply for a computer which already has a pre-installed version of windows vista ultimate running.
Steps to burn the vista install dvd (thanks to orev and seven11)
Click here
http://www.vlite.net/download.html to download vlite software.
Open vlite.
1. Browse and select the folder WAU (c:\windows\sonysys\WAU)
2. Select your version of vista. (existing version of vista)
3. Click the ISO tab on the left pane.
3. In the preceding screen, under the general option, select the mode direct burn. You can also select create image and save the iso image file. Insert a blank dvd.
4. Click burn to start burning the iso image in the dvd. It will take a while for the whole process to complete. Your vista install disk/upgrade disk is ready for use.
5. Exit the program.
Make sure you burn the recovery dvd's before the clean install process.
Back up your personal data.
I had referred Scuderia's (Gary) clean install guide for the sony driver/software installation and Orev's(Clean install guide in HP section) method for activation of windows vista.
Clean install instructions:
http://forum.notebookreview.com/showthread.php?t=145748
Activation backup and restore instructions:
http://forum.notebookreview.com/showthread.php?t=120228
Enjoy your new clean system with zero bloatware.