In the beginning, when it comes up and says

Windows XP
Windows XP VGA mode

Press F8 for advanced options

. . . . . . . .

It will also list Windows 98.

If you are really skeptical, just know that even if win98 were to fudge the boot up (which I'm sure it wont), you could use your Win XP recover disk and let it fix the MBR or at worse, re-install Win XP.

Again, though, I have a 98% certainty, which would be 99.9 except for the fact I Upgraded my Win2K installation on the machine configured with only WinXP and 98. (Meaning I did the side-by-side installation while the computer was in Win2K and not XP)

I can still boot either one.