Even though this is old news, I had not heard about it as copied from http://www.javaworld.com/javaworld/j...-gosling.html:
"September 9, 1998 -- Sun Microsystems Inc. Vice President and Fellow James Gosling, the co-creator of the Java programming language, told a court here today that Microsoft Corp. has compromised the cross-platform capabilities of Sun's Java technology by modifying it in a way that Sun never intended. "
This is probably the reason behind lack of support for java in XP. Microsoft tried to make it so java wasnt the free multiplatform thing that sun had envisioned. By making visual j++ microsoft tried to make it so you had to have their OS to use their java applications.