THINKPAD T,X series, not other series from Lenovo

My Thnikpad A31 (made in 2002)runing XP and PPstream is great;

My Thinkpad X61 tablet and my son's Thinkpad t401 is very stable.But DELL E6400 for working use had replaced screen, other DELL D610 motherboad was dead in 3 years.

All old Thinkpads are still runing XP in my office, while other laptops with different brands were sent to junk yard.