Clean install winxp from Vista?

As stated above, download XP versions of the drivers for your computer and save them before you start. If you can't find XP drivers then those devices won't work.

If the hard drive was formatted by Vista (e.g. if it came with Vista preinstalled) then you will have to reformat the drive as part of the installation process; Microsoft changed the NTFS file system between XP and Vista, so XP can't read a Vista-formatted drive. I found that out the hard way - tried to "downgrade" and the XP install kept failing.

If the drive was originally formatted with XP then you should have a choice during the install to wipe out the old Windows folder and install, or reformat the hard drive. If there are files you want to keep, just wipe out the old folder; otherwise reformat.

Yes this is pretty basic, I recommend downloading any drivers for your PC first, the best way is to go into your device manager (right click my computer, go to properties, click hardware sub-tab, click the device manager button) and make notes of the names of your major component names etc, EX. mother board, video card, sound card, network card (at least this one so you can connect to the internet and download the rest), than make sure you know the proper model number of your laptop. Save the drivers on a flash drive or CD so you can access them with your laptop without having the internet, than do a full format on your harddrive and install Windows XP.

"could n't the classes working properly under xp additionally run properly now under vista ??" you're able to think of so, yet Vista is a quantum bounce remote from XP. I wouldnt propose the improve till this is needed.... Many, many purchasers are "downgrading" from Vista to XP via subject concerns with Vista!

yes, there no problems, you might need to download the audio and wireless lan drivers form your computers website manually, this is not a problem.