Run msconfig from the run commapnd options in the windows startup. Make sure you have administrative rights.
Under the Boot Tab, you will see the whole list of those OS's , click on each unwated one and delete.
And set the Highlight one as Default.
Apply, OK and reboot. Check and see if it worked.
Or Else finally....
Then you need to edit the Boot.ini, system.ini or the win.ini file and delete those entries manually. Not the whole files, but edit them in notepad and delete the excessive entries.
i have no clue how to do that