This is how to do it in Eclipse 3, it should be pretty close...
In your Preferences>Java>Installed JREs, add the location of your Sun JRE Open the program you want to run, from the run dropdown, select 'Run...', select 'Java Applicatio', New, make sure the correct class is selected, on the JRE tab select 'alternate JRE' and select the JRE you just added.
Now when you choose to run this class it will run using the JRE specified and not the default (possibly IBM) JRE.
I hope this helps.
ps please reduce the use of contractions (4, ur, abt, rgds, u etc) They make posts harder to read and reduce understanding. Particularly for this site which has a high proportion of international visitors.