JAVA PATH

Computer->PROPERTIES->Advanced System settings->Advanced->Environmentvariables->user variable for ...->NEW->

then write Variable name as
CLASSPATH
and variable value as
.;C:\Program Files\Java\jre1.6.0\lib\rt.jar;C:\Program Files\Java\jdk1.6.0\lib\tools.jar;C:\Program Files\Java\jdk1.6.0\lib\dt.jar;

(ie write the full path of dt.jar,rt.jar,tools.jar)

then
from System variables
select path->edit->add one more line in the line Variable value
C:\Program Files\Java\jdk1.6.0\bin;

To test the installed java
run->cmd->c:/->java -version

To compile
javac nameofthefile.java

To execute
java nameofthefile