java doesn't work on my comp!

i have recently formatted my computer, and re-intalled everything back, i have windows xp running and i just downloaded the java v. 1.4 standard edition, but it doesn't seem to work, i don't know why, it does complie with javac but when i run with java <name> it throws and Exception in thread "main" java.lang.NoClassDefFoundError: with the hello.java!, I don't know what's wrong please help me out, i have already compiled it... if anyone is wondering.

[471 byte] By [doofiedoa] at [2007-9-27 8:33:43]
# 1
Was java working before you re-configured? Have you looked at... http://java.sun.com/docs/books/tutorial/getStarted/cupojava/win32.htmlThere is more to the error message than you posted. Please post the rest.
atmguya at 2007-7-8 16:44:01 > top of Java-index,Developer Tools,Java Compiler...
# 2
i did re-configured it, i formatted my comp, but still doesn't work i think there is a problem with windows xp, or with java 1.4 i'm gonna try to redo everything, with java 1.3 i'll post any changes.
doofiedoa at 2007-7-8 16:44:01 > top of Java-index,Developer Tools,Java Compiler...
# 3

Still doesn't work! i don't know why... if anyone can help me out...

i compile a simple program on win 98 and it runs with java 1.3;

now on win xp i compile the program and the .class is created but when i run the java and name of the program it gives me the -java.lang.noClassDefFoundError: <name> i don't know what is it...

doofiedoa at 2007-7-8 16:44:01 > top of Java-index,Developer Tools,Java Compiler...
# 4
I have jdk 1.4 and windows xp. I don't have any problems. The Classpath on XP is accessed thru ControlPanel - System - Advanced - Environmental Variables. If you have a Classpath setting, be sure . and the directory where your hello.class file is are in the Classpath.
atmguya at 2007-7-8 16:44:01 > top of Java-index,Developer Tools,Java Compiler...