Hi

How to install grub in /sdb3 /media/{some-uuid} via Live CD?

# mount
# -> /dev/sd3 /media/{some-guid}
# grub-install --force --root-directory=/media/{some-guid} /dev/sda3

Thank you.

Which Grub are you using? Grub Legacy? Grub2? Which distribution of Linux? What have you tried? What happens when you try whatever you have tried? Any output? Error messages?

I use F15, in dual boot with win7. After boot I'm prompting with grub> command line. So, I use Live CD ..

# grub-install /dev/sdb3
-> /dev/mapper/ ../dm-0 does not have any corresponding BIOS drive
# grub-install --force --root-directory=/media/{some-guid} /dev/sdb3
-> Unrecognized option `--force`
# grub-install --root-directory=/media/{some-guid} /dev/sdb3
-> /dev/sdb3 does not have any corresponding BIOS drive

# grub --version
-> grub(CNU GRUB 0.97-71.f15)

From grub> command prompt I have tried
# root (hd0,2)
-> Filesystem found
# kernel /bo[tab]
-> Could not mount filesystem

Did you have windows 7 installed and working for some time?
Is this a new installation of Fedora?
Were you ever able to boot into Fedora?
Fedora uses Grub Legacy.
How many physical hard drives do you have? Your output shows trying to install grub to sdb3 and sda3 which would be the third partition on the second hard drive and the third partition on the first hard drive. You probably did not install Grub to the master boot record? Were you planning to boot both systems with the windows bootloader?

Use the Fedora CD, open a terminal and log in as root (type: su -) and enter this command to get partition information to post: fdisk -l(that is a lower case Letter L).

Posting the contents of the grub.conf file from the installation would be helpful. Do you know how to mount partitions/filesystems?

I am not sure about /dev/sdb3
I think it should be
to install to MBR .
/dev/sdb3 would install to superblock of the sdb3 partition and not to MBR of the sdb drive I think .

this '0' means sda and '2' partition 3

To me it looks like you want to boot the HD by the MBR of the USB pen .

Is this UUID correct ?

would show the UUIDs of all partitions of /dev/sda .