j'ai eu le meme probleme j'ai vu la solution dans :
http://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=115980
En fait il faut changer un parm du BIOS tout simplement :
------- Additional Comment #15 From Radek Vendelberger on 2004-04-27 11:59 -------
I solved this problem on my computer.
FC1 and windows on my comp boot fine both, but if i upgrade to FC2
test1, so windows boot manager dont load. I tried reinstall both
systems, repartitioning whole disk - nothing, after i install grub,
windows boot loader dont start and this problem dont solve fdisk /mbr.
All that you need is set your disk to LBA mode in BIOS. Dont leave
there AUTO. Thats all. Linux read BIOS access mode wrong and grub
setup something wrong on MBR - its why windows boot manager cant be
find in MBR and windows cannt start.
Attention. Please, check what access mode you realy normal use to
access disk. Changing access mode from Large to LBA for example can
lead to lose data from your disk!
If you use another access mode than LBA and setting them in BIOS
doesnt work, try backup your data and repartitioning disk in LBA mode.