What about setup (hd0)? Can you get to a Live CD and then press C to get to a GRUB command prompt, then just type in setup (hd0) to place the boot loader on the zero (first) disk? Assuming there are entries out there in your GRUB menu and the boot loader is still present, that may be enough.
If not, you can use other GRUB command entries to locate partitions, and if necessary, create menu entries to access them. Unless you also removed some software, you should still have XP on sda1 and Fedora on sdb1.
You can get at them interactively this way if things are not too badly messed up:
title Windows XP on disk 1
title Fedora on disk 2
Put these entries into the /boot/grub/menu.lst file when you can get at it. In the meantime, you need not enter a title line - it is just for display in the menu. Use the chainloader to get to one system or the other. They should both still be there, unless other unintended things have also happened.
You can also search for actual partitions and actual files by doing the following:
Enter GRUB interactively, as suggested above.
For the root line, enter root, then enter a ( and press Tab. A list of device types will appear - hopefully hd would be one of them. Put in hd and press Tab again. Now you should see which disks are available. I would expect to see 0 and 1, based on your description. Select either 0 or 1 and press Tab again. Now you should see the available disk partitions for the disk that you chose.
You can do the same thing if you want to manually create your own boot and initrd lines in GRUB interactively. This is a great way to get your menus right - first figure out where things are interactively, then note them and add the correct entries into GRUB once you have access to the /boot/grub/menu.lst GRUB menu.
Hope this gives you some ideas.
is the definitive GRUB manual. It might be intimidating for the newcomer, but it certainly is comprehensive. Ask any questions and I would be glad to help out.