Hello Alejandro,
I would suggest the Demudi installtion did not write a correct grub
configuration. Please post your current configuration, so we can see
what's going wrong there.
If you would like to rebuild your entire system I would suggest the
following layout:
hda1 - ntfs win xp
hda2 - linux (which whatever filesystem you prefer)
hda3 - linux swap
hda4 - fat32 (if you need it, for example xp/linux shared disk)
You should install windows first, let it repartition the entire disk and
then continue with the linux installation. But if you're satisfied with
your current layout, it should be managable with a correct grub
configuration.
--
---> doj / cubic
---->
http://cubic.org/~doj
----->
http://llg.cubic.org