We've not tested SE 5 on Vista, so that combination is not officially supported.
SE 6 will officially support Vista.
We can say that we have 1 Vista machine here where we installed SE 220.127.116.11 AS running with its built-in webserver
and it works fine for light development use. You are welcome to install SE 5 on a Vista machine and see how it goes.
The only issue we found is that Vista has IPv6 support enabled, and SE 5 does not fully support IPv6.
To better understand that issue and how to get around it, please see SE FAQ #347