OK, this is how I did it:
I was unable to compile ReactOS (strange errors during compilation). So I got the ReactOS version preinstalled in qemu. I used WinImage 7.0 (It's shareware, I don't know any free HD (FAT32) disk image editor
) to extract the ReactOS folder and binaries inside it to my C: drive. I also extracted "Documents and Settings", FREELDR.SYS and FREELDR.INI. - I don't have the "Documents and Settings" directory 'cause I'm using Win98.
Next, I tried to use Grub for Dos to boot FREELDR.SYS from MS-DOS mode - no succes. It could load Freeloader, but always locked at the "Detecting hardware..." message.
So I tried a different approach - that worked! I thought the problem was related to Dos Grub, so I tried to load FREELDR.SYS in a different way. I downloaded an old Freeloader (FreeLoader-20041226.i386.tar.gz) and then I tried to run the program install.exe, which is part of the freeloader package, to rewrite my HD bootsector, in order to load FreeLoader properly. I didn't work again. I couldn't even rewrite the floppy disk bootsector, it always failed! Then decided to look at install.c to see what it was doing. I found out that it was trying to rewrite the first floppy sector, but wouldn't touch the BPB (Bios Parameter Block, I guess). The floppy disk BPB starts at offset 3 in the boot sector and is 59 bytes long. So I did it manually, using WinImage. That way it worked.
After patching the boot record, I copied FREELDR.SYS from C: to A:. Then, I copied the FREELDR.INI which came with the old Freeloader to A: too. That's it.
I'm sure there should be an easier way to do that, perhaps rewriting install.exe (Maybe it works ok on WinNT, remember I'm using Win98), but if you want me to post a message about how to use WinImage to manually patch the bootsector, please ask me. There should be a way to patch your HD MBR also, but I don't think WinImage will write directly to the Hard Disk. A DOS program running in DOS mode could do it!
About the WIKI... I think it will be nice to write one, but first I want to hear what you think abou this method. There should be an easier method b4 we post it the wiki.