check here:-
http://www.mcse.ms/message349955.html
check point:-
'When the problem occurs, press Shift +F10 to bring up the
command prompt. Then type taskmgr.exe in the DOS window
and press Enter.  The Task Manager should be started. If
not, try to press C+Shift+ESC. In the Task Manager
program, select the error messsage window in the
application list and click "End Task". In the process
list, terminate the unregmp2.exe program. Exit the DOS
prompt window and resume the installation process.'

regards,