Nothing after admin login
I have a DELL Dimension 3000, Intel Celeron 2.4GHz, 1GB RAM, 70GB drive with over 55GB free.
I have used the 'Windows Installer" to load ubuntu 12.10. The install goes okay. I get the choice to boot to either Windows XP Pro or Ubuntu when the machine starts. When I try and run Ubuntu I get "The application Compiz has closed unexpectedly" error. After that the login screen shows, but if I try and login all I get is the blank desktop. After a re-boot, the ubuntu login screen shows, I get a "System program problem detected" error message.
I have been prompted to instal a update to ubuntu, which is strange.
How can it be working enough to tell me an update is available but the desktop is not showing?
The PC doesn't have a DVD player so I can't try loading it from that, and until I know that it will run I do not want to delete the Windows XP Pro. Its a spare PC so there are no files on it. I've done a windows update, Java, and Flash, as well as a Defrag. The Windows side is running fine.
I am a Mac guy with a good amount of Windows experience but I am new to Ubuntu.