Yes, Xandros can coexist on a system with Window Vista.
However, there are a couple of steps that need to be followed to make this happen.
Unlike with previous versions of Windows, Xandros Desktop can not resize the Windows Vista partition during installation.
You must follow these steps to ensure you do not damage your Windows data.
Prior to installing Xandros OS, users should use Vista's Disk Management tool to re-size the Windows partition:
Boot into Windows Vista
Select Start | Control Panel | System and Maintenance
Click "Create and format hard disk partitions" under the Administrative Tools section
Click Continue
Right click a Windows partition and select Shrink Volume
Follow the prompts to re-size the partition
Reboot the PC with the Xandros Installation CD in the CD drive.
Install Xandros Desktop OS