XP does not dual-boot if Win98 not in the "Normal" folder.....

OK - I've done dual boots in the past, so I know the
basics. Here's the problem I have now: I already have
Win98 installed, but it's been installed to a custom
folder, NOT the standard C:\WINDOWS. I start to install
XP using the ADVANCED (New) installation option, but it
doesn't seem to recognize that Win98 is also installed.
The end result is that my computer loads and runs Windows
XP only, but the Windows 98 installation is still on the
hard drive. There is no boot menu... it seems that
Windows XP will only dual-boot with 98 if it can find Win
98 in it's default folder while you are installing
XP..... Any thoughts? Can I tell the XP installation
where to find my 98 O/S (specify a location) before it
installs XP?