If the machine does what you want it to do, I'd leave it alone! If you can add a wi-fi card and you want to, do it. "Favors" gets us into existentialism. Lets not go there!
I do not think you can just install Win98 over XP. You would need to
reformat and start from scratch. 98 uses FAT file system and XP uses
NTFS. Win98SE uses NTFS but otherwise, you will nee to convert. Hardly seems worth the effort. You would lose all your files, for one thing.
I HAVE A GATEWAY SOLO - MODEL 9150 LAPTOP @ 333 MHZ. I ADDED XP A COUPLE OF YEARS AGO AND ALL THE MEMORY THAT I COULD. THE MACHINE SLOWED RIGHT DOWN BUT IS STILL USABLE FOR WHAT I NEED IT FOR. I NOW WANT TO ADD A WIFI CARD AND IN THE PROCESS OF SHOPPING I WAS TOLD THAT I DID THE MACHINE NO FAVORS BY ADDING XP, AND THAT I SHOULD GET RID OF XP AND GO BACK TO WINDOWS 98. I HAVE NEVER RUN A REGISTRY FIX ON THE THING. SHOULD I RUN A REGISTRY FIX TO TRY TO SEE MORE SPEED AND LEAVE XP ALONE WITH A NEW WIFI CARD OR ELIMINATE XP? IF SO, HOW DO I GO FROM XP TO 98?