I have tried several times to install Natty on its own partition on my laptop (WinXP, Intel x86) using UNetBootin, but it always fail.

There is a dialog box:

Failed to unmount partitions



The installer needs to commit changes to partition tables,

but cannot do so because partitions on the following could

not be unmounted.



/cdrom



Please close any applications using these mount points.



Would you like the installer to try to unmount these partitions again?

If I click on "continue" Ubiquity will hang up, that is, the slideshow will play forever. I do not have a built-in optical drive and I'm not currently using any peripheral.

I have tried sudo umount /cdrom it says that cdrom is busy. Then the command fuser /cdrom returns "Stale NFS file handle".

How can I work around this to install Ubuntu?