Problems due to installing softwaare

[valhalla2100 at comcast.net]

Hello,

I decided to enhance my Ubuntu experience by downloading
software from one of the tabs that I found.   

Today I booted up and got the Xubuntu image.  The screen
then went blank.  Rebooted and still the same problem.  

I noticed on the boot option screeen that I still had the
other one listed.  Attempted to launch the 9.04 version
and the sceeen went blank again.

I tried to do solve the problem in the recover mode but
ended up removing my original 9.04 list on the boot screen.

Does anyone have any ideas if I can recover?  

Someone recommended a free Ubuntu book for O'Riley.  That is
not accessible.

I am using the try out mode from the CD.

Thomas