i'm assuming that your java installed
at c:j2sdk1.4.2_06,So configur it as per your installed directory..

Open your C:autoexec.bat file in edit
mode. by defaulte it is in hide and readonly mode.. so make u it
visible and uncheck the read-only before you start edit it.

Append the following 3 statement....

SET JAVA_HOME = "c:j2sdk1.4.2_06";

SET CLASSPATH =
%JAVA_HOME%lib ools.jar;%JAVA_HOME%libdt.jar

SET PATH = %PATH%;%JAVA_HOMEin%

now you make the autoexec as readonly
and hide mode...

in your are using windows xp, 2000 or
NT, then follow the following steps to confogur your java...

1. On you desktop , Right click on
you MyComputer Icon and select properties

2. Select Advanced>Environment
Variables

3. There your have two boxes, select
New button on Sysetm variable box and give variable name as
"JAVA_HOME" and value is "c:j2sdk1.4.2_06".

4. Select "path" variable
(it must be there in the existing list),and select edit, append "
;%PATH%;%JAVA_HOMEin%; " at value part.

5. Select "New" button and
CLASSPATH as a variable and "
%JAVA_HOME%lib ools.jar;%JAVA_HOME%libdt.jar " as its
value...

thatz it..