[gandip]

HOw can install vista in my XP .Is there any way to have both vista & XP. in one computer

 

[osbenje]

if you have multiple hard disks or partitions you could boot to XP then start the install of vista specifying a seperate drive/ partition for Vista to install to.

 

[sobeit]

see this for steps in dual booting.

 

[ob_kook]

You could also use MS Virtual PC (http://www.microsoft.com/windows/products/winfamily/virtualpc/default.mspx).

This is a great way to seperate applications and manage different O/S very easily.