Alrighty. Lets take a crack at this.
What it sounds like is that Redhat screwed over your MBR, so when the computer then, upon rebooting, found a list of, nothing to boot. However, it seems you then furthered the problem, by attempting to fix it by installing XP on a second hard drive, therefore further screwing over and already screwed up system. So basically the XP re-install might have been a real bad idea. But, a few things for you to try.
First thing. Make a Windows XP boot disk.. or just, use a Win whatever boot disk. Boot up the computer with it, and try "fdisk mbr". That resets the operating system table and lets the computer reset the whole darned thing by itself. You may want to remove the second, working, hard drive before you do this, so it only has the one disk to find an os on.
If this doesnt restore any kind of order.. well, your files are gone then. This is why you should backup files...
But, in an attempt to recover them. Try searching for the program "aefdisk". Put it on a boot floppy, and see if it can find the old hard drive/partition for you. If it, or any other program can find the old windows partition with all your files. Delete it. Make a new partition, and don't put anything on it. Then go hunt for any old file recovery program of your choice, run it on the drive, and see how much it can yank back out of it.