Presumably you did this through Windows and was guided through setting
up where you set your location, size that you wanted to allocate to
Ubuntu, user name, password etc ? So now you have the choice of going
into Windows or Ubuntu when the PC starts up but the Ubuntu side
sticks at the purple screen and doesn't go any further ?

Might just be that the installation didn't work and when doing it
through Windows it's a good idea to defragment the HD first as this
will help in the creation of the special file that Ubuntu run in when
installed in this way.

You can delete this Ubuntu file from within Windows and then run a
full defragment and try the installer again. Also make sure you have
enough free space on the HD for the size of the Ubuntu you set. Last
thing you want is to allocate so much that Windows doesn't have enough
to work with !