Umm...
twiztidtruckie... do you know what you're talking about when you say it will slow your computer down?
Installing 98 on a second partition won't affect the speed of either OS.
Also, it will not automatically dual boot if you install 98 after XP, 98 will overwrite the winXP bootloader. My favorite method of dual booting is to install
XOSL to the fat32 partition (needed for win98 anyway) and set it up right, it's pretty self explanitory, just follow the directions.