General Description: Coregen tries to start up but just hangs at the point at which it is supposed to be loading SizeRequirements.class (the information that it is trying to load SizeRequirements is only evident if Coregen is invoked in verbose mode by editing coregen.bat and adding a -v option to the jre.exe invocation line).
The problem is due to a conflict with a "JavaHome" setting in the Windows registry. Coregen can only start up after this entry is removed.
Rather than remove the entry entirely, you may back it up by exporting it to a register file.
To edit the registry,
Go to the Start Menu and select "Run".
Type "regedit" in the field marked "Open:" and click OK.
Navigate to: HKEY_LOCAL_MACHINE/Software/JavaSoft/JavaRuntime Environment/1.1
Select the "JavaHome" register entry and select "Registry->Export Registry File..."
Save it to a name and location of your choice (suggested name is JavaHome.reg).
Finally, delete the register entry in the ... JavaSoft/JavaRuntime Environment/1.1 folder and restart your PC (or simply log out and log back in if you are on Windows NT).