Exception in thread "main" java.lang.NoClassDefFoundError:

i getting above error while trying to execute the sample java programe.

Compilation went thru fine.

java environment details of my PC  as below ........... Please advice the solution
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C:\>path
PATH=C:\Program Files\Java\jdk1.6.0_21\bin;C:\jdevstudio10133\jdk\bin;C:\OracleF
MW\as_1\bin;D:\dev10gHome\jdk\jre\bin\classic;D:\dev10gHome\jdk\jre\bin;D:\dev10
gHome\jdk\jre\bin\client;D:\dev10gHome\jlib;D:\dev10gHome\bin;D:\dev10gHome\jre\
1.4.2\bin\client;D:\dev10gHome\jre\1.4.2\bin;C:\orant\bin;C:\WINDOWS\system32;C:
\WINDOWS;C:\WINDOWS\System32\Wbem;C:\orant\jdk\bin;C:\Program Files\Windows Imag
ing\;C:\Program Files\Investintech.com Inc\PDF2Excel;C:\Program Files\QuickTime\
QTSystem\;C:\OracleFMW\as_1\opmn\bin;C:\OracleFMW\as_1\opmn\lib;C:\OracleFMW\as_
1\perl\bin;C:\Program Files\Java\jdk1.6.0_21\bin;C:\jdevstudio10133\jdk\bin;D:\d
ev10gHome\BIN;;C:\Program Files\Java\jre6\bin

C:\>echo %CLASSPATH%
.;C:\Program Files\Java\jre6\lib\ext\QTJava.zip;C:\jdevstudio10133\jdbc\lib;C:\j
devstudio10133\jdbc\lib\ocrs12.jar;C:\jdevstudio10133\jdbc\lib\ojdbc14.jar;C:\jd
evstudio10133\jdbc\lib\ojdbc14dms.jar;C:\jdevstudio10133\jdbc\lib\orai18n.jar;C:
\jdevstudio10133\jlib\activation.jar;C:\jdevstudio10133\jlib\javamailintegration
.jar;C:\jdevstudio10133\jlib\mail.jar;C:\jdevstudio10133\lib\servlet-api.jar;D:\
JavaProg;

C:\>echo  %JAVA_HOME%
 C:\Program Files\Java\jre6

C:\>