The short version: It sucks.
The long version:
I wouldn't really do it if it was just about me. But my aunt will start using this old machine so it's not practical to convince her to use Linux. After all, I will be quite far away from her so tech support will be an issue. Anyway, I am getting really pissed off.
For starters, on Linux we have live CDs which can be installed immediately to the machine. And if the machine (like my netbook) has a faulty external DVD/CD drive, we could still manage to install a Linux distro. Converting the disc image into a bootable USB installer isn't as convoluted nor as tedious nor as long as converting a Windows XP installer.
I suppose people will say it's because it was not meant to be used this way. True that. But still. It's really getting on my nerves now. ~_~ So the next time someone asks me if I could help them convert their old Linux machine to Windows XP, I'd probably not do it unless I have REALLY PLENTY of TIME. And if it's not a case of something similar to my aunt, I will just help them find a good set of tools for their needs.
Komku is the tool I am currently using for this process. I will bookmark the link but I am crossing my fingers that I will NEVER have to do this again. ~_~ details later.