new installations wiped out after reboot

A CLIENT BROUGHT ME AN ACER EXTENSA 5220 LAPTOP WITH WIN XP ON IT (THOUGH THE LAPTOP HAS A WIN VISTA STICKER ON IT). HE WANTED ME TO INSTALL SOME APPLICATION PACKAGES ON IT, TO MY AMAZEMENT, EVERYTHING I INSTALL GETS WIPED OFF AFTER A REBOOT OF THE SYSTEM, I HAVEN’T SEEN THIS TYPE OF ISSUE BEFORE.
CAN ANYONE PLEASE HELP ME OUT?
COS I’M IN DARE NEED OF ONE,
TANX.