It might be a good idea to make an image of the original drive just in case; look for Powerquest Drive Image which often turns up on cover CDs. The version in PCAs Downloads section predates XP.
A search for Evesham on this forum reveals largely positive comments about its customer service, but not much about the laptops. If they are as good as the desktops, you'll be fine, but there is no guarantee of that of course.
As for warranty implications, you would be best off talking to Evesham, explaining your plans exactly.