The “WUBI” installer, which allows you to install Xubuntu etc inside Windows Vista is not included with the latest distro (12.04), so what can you do?
The first option, is to install an earlier version, say 11.10 and go for the “Distribution Upgrade”.
A drawback with WUBI is that it creates a very large file called “root.disk” which contains a disk image of your Linux installation. If you get an error on this file, you sometimes cannot recover your data. This does not happen very often, but using WUBI, there is a definite risk of a loss of data.
So what is the alternative method?
The method I used was to use “EASEUS Partition Master 6.5.1 Home Edition” (Freeware) to create a blank partition of 10 gig within the “DATA” partition on my Vista Laptop. Then I downloaded Xubuntu 12.04 “alternate” installer.
I then used the alternative (non-graphical) installer to erase and partition the 10 gig sub-partition I had created. The installer creates the sub partitions within this partition i.e. the “swap”and “home” partitions.
Warning: it is very easy to erase your Windows installation by mistake! If you are not at all sure, choose “go back”!
It is easy to tell which partition is which because you know if you created a 10gig partition, the size of the partition must be this value, or approximately this value if you did not specify 10gig exactly. If the value is the size of your whole drive, then it is the wrong partition, and you don’t want to format it!
To understand the procedure without running the risk of wiping out your Windows installation, insert a 4 gig or larger size USB flash drive and use the Linux installer to partition and install to the USB flash drive. You can then set your machine to boot from that as a test.