If you have a friend with a Vista disk just borrow & install it.
When it asks for the product key at install leave it blank. This will give you the option to install
any of the different versions of Vista.
After 30 days you will have to put in a key and activate the software. However if you are just trying out different versions you will not need it to be installed for more than 30 days.
N.B. If you install the Premium version (for example) & then put in and activate with a Basic version (for example) key you will get all sorts of problems.
This way you can try all of the versions before buying the one you want.
Steven