Thank you for your post.
The minimum system requirements for Windows XP and Windows Vista are a bit different.
Pentium III 800MHz 32-bit or higher (500MHz for XP)
512MB of RAM (256MB for XP)
If you have met these minimum requirements, then review Knowledge Base Article #7016
If this does not help, see if you have access to another Windows Vista machine. Try installing on that machine. If successful, you can then determine what is different between the two machines.