dont worry , i think u chose linux loader during install . LILO causes this problem , and i faced it first time i installed it , so it freaked me out then
. So if u have win98 or xp , use the cds to boot and run fdisk /mbr or fixmbr respectively . Regarding xandros , ur partition would be safe . if u have win98 , theres a way to boot into xandros without using boot loader . else , just install grub from xandros . there are plenty grub faq's in the forum . Do tell which os u got to continue