If your askiing will my system run XP then, put the xp disc in and run the compatible tool, it will tell you have a any issues, I made that same step many years ago and my pc runs xp fine
Do you want your windows 98 interface to look like the interface in XP? Do you want this system wide? Or just for a specific application you're programming? If so, which language are you using? If not, there is no skinning software like WindowBlinds build for windows 98.
I believe there is an older version of windows blinds for Windows 98 and an XP Theme for it. It's been a really long time since I've used it, and I no longer have the installer for it or anything.
I don't really see why you would want to keep using Windows 98 though.. it's pretty old and outdated now.