How to use mssql as database for my site running on redhat linux
Once your new server is running, you only have to do a few things.


Dump the old database (PgSQL)
Convert the dump to MSSQL
Import the dump.


If you search on google you should be able to find tools that will allow you to export convert the dump. This is not perfect but is probably the easiest solution.

Alternatively if that doesn't work, you can create a script that from within Drupal fetches data from one database and then inserts it into the other database, effectively using Drupal/PHP to translate the dump. This is much slower and requires more work, but have less chance of failure.