I have a similar problem....
I have a Compaq Preasrio (Celeron).
It initially had XP on the primary master... and I attempted to install FC5 to the primary slave.
After the shut down... it boots into windows...
I booted from the CD and tried to install GRUB an overy possible combination of hda ( XP) and hdb (FC50 but as soon as it gets to the "upgrade installation" it tells me No kenal installed. the boot loader configuration will not be changed ( or something to this order).
No matter what... it will not allow me to multiboot.
So thinking I was a clever dickens... knowing that GRUb should load XP.. I swapped the IDE cable on my hard drives.. technically reconfiguring them ( black for master, grey for slave).
I boot up.... Error Loading Operating System. No problem... in this new configuration, I reload FC5 onto the new master disk.. and I got to see Linux for the first time ( yaaaaay)... however when I enter the GRUB menu... Windows shows up as "other"... and atempting to boot into it just gives me two lines in the kernel
noverify(0,1)
chainloader +1
I once again try to change the bootloader... and nada... it refuses to boot into XP.
I tried every possible combination of reinstallation of the bootloader from the Upgrade menu and it refuses to alter the boot loader... and I can't get in to XP from the GRUB.
Any suggestions would be HUGELY appreciated. Right now. I'm actually swapping the hard drives when I want to go back and forth.. and that can't be the best way to do this.
Thanks
Ed