Sry for making new thread
Hmmm... are we being a bit too strident about telling people to be careful about making new threads?
It sounds like ubuntu is installed, and when you boot for the first time, it stops with GRUB Error 21. Is this correct?
Or do you mean that you cannot boot the desktop CD?
The error message is:
21 : "Unknown boot failure"
This error is returned if the boot attempt did not succeed for reasons which are unknown.
It helps if you can be exact about what the full error is and when it occurs. Also, please, provide a link to that other solution you did not understand... you cannot install ubuntu to HDD if all the HDDs are disabled.