It seems that you are asking two different questions here. One is how to get your programs to compile and run using a DOS prompt and the other is how to get your programs to compile and run using Eclipese.
To get your programs to compile and run in a DOS prompt you can follow the instructions on the
CattleDrive intro page. These instructions are just as valid with WinXP as they are with Win9x. It appears that MS overwrote at least your classpath (and maybe your path) when you installed it.
Your path needs to include the subdirectory that contains javac.exe (usually jdk_home\bin), and your classpath needs to point to the subdirectory where your compiled classes are. If you follow the directions on the page I mentioned, they will be in C:\Java, so C:\Java needs to be in your classpath. (jdk_home)\jre\lib\est can sometimes be used for *.jar files, but that is beyond our current subject under discussion.
I have no experience with Eclipse, but most IDEs require you to set your sourcepath and your classpath (again) within the browser. For more help with setting up Eclipse, you might want to pop over to the "IDEs and other Tools" forum.