I'm having trouble installing Ubuntu on my laptop..

I'm installing from my hard disk using UNetbootin and keep receiving the following error when the installer is attempting to partition the disk:

Failed to unmount partitions

The installer needs to commit changes to partition tables, but cannot do so becaue partitions on the following mount points could not be unmounted:


Please close any applications using these mount points

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

There is an exisiting XP install on the drive, and I have tried various combinations of new partition tables and deleting existing partitions, to be reformated by the installer, to no avail and keep receiving the same error.

Any help welcome!