a "proper mastering program" just means a CD/DVD Burner program that is
seperate from your OS.

until you locate/obtain a program (i highly recommend Nero 6), you could use
"CDBurnerXP Pro", which is a free program, on the XP machine to burn a
standard CD.
http://www.cdburnerxp.se/

the Windows 98 system may have an issue with the disc. it may not read RWs.
also, im not too familiar with how WinXP deals with RW discs, but it may be
using a packet writing method - similar to InCD or DirectCD, or other apps
like that, which try to treat CD/DVD-RWs as floppy disks and similar storage
devices. in that case, proper packet writing software that is able to read
the XP made disc would need to be installed on the Win9x system.

i dont do "drag n drop" burning, and i think i may have used Windows XP's
built in burning once.

It's not the program that's important, it's the format that you create the
CD in.  You need to create an ISO 9660-standard CD, commonly known as
CD-ROM.  Your CD recorder was supplied with CD writing software that can
create CD-ROMs. The process involves setting up a list of files to be
created on the CD, then telling the software to create it.  For maximum
compatibility, be sure to create a closed-session CD - some programs close
the sessions automatically, while others have it as a separate step.