If so then follow these steps:
Right click on My Computer > Properties > Advanced Tab > Startup and Recovery > Uncheck the "Display List of OS for 30 seconds" or whatever it may be set for.
may be something to do with the boot.ini file. when you go into msconfig -> boot.ini tab what do you see there ? could you post it here. that would be helpful.
yes, check the boot.ini file
if your previous version of windows was say windows 98 and your new version of windows is windows xp.
then delete the line which has windows 98 in the end.