Make sure that your java install is in the path
right click on my computer, choose properties, advanced, environment, system, and set the path to your jdk

I have installed Java VM but the error is occurs. Pls advise.

Just because there is an error message: "Java Virtual Machine Launcher. Cannot find main class. Program will exit.", it does NOT necessarily mean your java is corrupted/missing that you have to reinstall (although this is an trivial assumption, which is most often wrong).  
In this case, it means there is a program that's being booted at start-up (most often spyware/adware that you do not want in the first place) is missing (i.e. program was deleted by running certain spyware/adware sweep), and this program requires java.  Of course, this program could be a legitimate program too that you accidently deleted from c:\Program Files\.

Solution:
start -> run -> msconfig. Select Startup tab.  You will see a number of programs that would run at startup.  One or more of these would have a java requirement, usually indicated at the beginning of "C:\Program Files\..." listed under the Command header.  If it's a legitimate program that you accidently deleted (maybe just the ".exe" file that's missing), resinstall it.  If it's spyware/adware, note the name of the program, uncheck the box, then hit apply.  Restart the machine.

If you really want to eradicate the spyware/adware from your machine, do not restart yet, go to the next step.

Next step:  Registry cleaning.  
start -> run -> regedit. Then Edit -> Find -> enter the name of the spyware/adware then search. When found, hit Delete key, then Enter (OK).  F3 to Find Next, then repeat the delete until you wipe it out.  To be safe, do not delete the entire folder, just do the specific reg keys because some may be used by other programs.  If you are unsure, don't delete.

I always clean my registry after I uninstall a program.

Hi guys, im having the same problem, and i my guess is that everyone is having the same problem as mine, meaning that the application thats causing the problem is javaw.exe i found out by printing screen before and after the error screen while observating the TASK MANAGER,
maybe some malware is causing it but not sure cuz niether adawre nor spybot is getting them nor CWS or norton so...
im going to try to unistall and then install again ill let you guys know

cya

nop, jeje didnt work
dont know what to do now except sending an emial to java.com

ok guys fixed my problem in a jiffy, my problem was that i had a file that i had erased accidentaly so when i did that without uninstalling the startup option was still there, so when i checked msconfig on startup tab the file was there, how did recognize it? becuase on the command it appears first the directory of javaw.exe and then the programs name(that i deleted accidentaly) so all i did was install the file again in the same folder that was before i deleted tit accidentaly.
if you cant resolve it this way download adaware, spyboy search and destroy and CSW shreder, update them and run them it has to do the trick, finally run norton.

good luck.