Hi. ill just give you my 2 scents.
Putting a hard drive with a operating system already installed on it into a new computer with a different mother board and different cards is usually not a good idea. it probably will work in the begining, but you will run into hardware conflicts later on. the best thing to do if you have the windows 98 cd. is to reinstall it on your second harddrive. To do this, first connect your 2nd harddrive to your computer with Winxp on it and transfer all of your imortant data to the xp hd. then disconnect the xp hd from your comp (leave the 98 hd connected), use fdisk or something else to format the 98 hd, (re)install 98 and all your dirvers on it. Then reconnect the xp hd and transfer all your important data to the 98 hd. ( if your comp keeps booting xp, try to select the 98 hd from the boot menue or goto the bios and make the 98 hd your 1st hd, or make it master on the jumpers and on the cable)
i hpe this helps.
