check your grub.conf file
Check your grub.conf file. Under title other it should have
(hd0,0) is the first partition on the first drive or C in windows langauge. If you have (hd0,1) that would explain your problem and you can change it to (hd0,0). If you have something else then you have a bigger problem.
dual boot using grub (fedora and windows)
oh... there is a simple solution. i had pretty much the same problem a week ago. i spend amost a week to resolve that problem; however, the resolution was very simple.
>> go to the BIOS setting before you start your OS.
>> check you hard drives and change the type of detection the primary hd, AUTO to LBA.
>> and save it, and reboot.
you will see your windows is working now.
this problem is that GRUB doesnot correspond with some BIOS, so it doesnt not get the right partition table. which means it skips the first /dev/hda1 --> windows partition(LBA). GRUB starts to read the table from the second partition, /dev/hda2 or /dev/hdb1--> might be /boot of your linux distribution.
try it. you do not need to reinstall any of your OSs.