Thank you, guys.
I managed to create WinXP partition and dual-boot with Boot Magic (came with my old Partition Magic). This turned out to be helpful. Firstly, I could not install WinXP from Win98, because Win98 cannot read Japanese!

Therefore, I had to install before my computer loads Win98, so I needed a new partition and boot setting for that. Also, after installing WinXP, my machine only loaded from there, and not from Win98. As my main Windows should be Win 98, I used Boot Magic Rescue Diskette to force my machine to start from Win98, then reset the setting of Boot Magic.
My computer is now bilingual.
