Hi all! A couple of days ago I tried a dual boot with these OS. Having put Win xp on C partion and Win 98 SE on D, I've soon realized that nothing was right: Win 98 has obscurated (sorry, I can't find a better expression) Win XP, although they were on two different partitions, both with the same filesystem (Fat32). What is the solution? if you have a standard solution, please let me know.
Windows 98 changed the active partition to its own when you installed it, which is why it will only boot 98 now. You can fix that with fdisk from the Win 98 command prompt. Set active partition to #1, and then it should only boot Win XP.
Then, it should be possible to set up Win XP's boot manager for dual boot, but I don't know exactly how.
If the machine is a reasonably powerful one (more than 512Mb RAM and a good processor), then there is a better option. Use virtualization software to run Windows 98 as a virtual machine from within Windows XP. I run Windows XP under Linux using VMware Server [vmware.com], which is a free download also available for Windows.
Simply install Windows XP, install VMware server, create a new virtual machine and install Windows 98 in that machine. You can then run both OS versions at the same time without rebooting.