Hello champ1234 ,
You would be unable to use .htaccess in Windows plans due to the way that IIS works vs Apache.
You can set the order of pages searched for index page by doing the following:
Login to Plesk
Click your domain
Click Web Directories
In the section labeled Documents, you can set the order of which files are searched. If you want index.aspx, instead of index.html, you would make sure that the index.aspx is above index.html.
As test.aspx does not exist, you would need to add that in the same section.
I hope that this cleared up any confusion.