If your website is built on a Microsoft technology and its growing you need either a windows VPS or a dedicated server to host it. Here are some options for VPS windows hosting providers :
Accuwebhosting.com
Accuwebhosting.com offer 2 VPS plans on their windows server and the starting ( Super Economy VPS – 1 plan ) costs just $7.99 per month (If you sign up for at least 1 year). This plan comes with 50GB disk space, 500GB bandwidth, 1GB guaranteed RAM and 1 dedicated IP. Visit Accuwebhosting
Liquidweb.com
Liquid Web’s managed windows VPS plans are available in 1GB, 2GB, 4GB and 8GB setups and all come with a 100% uptime guarantee. Their starting VPS plan costs $50 per month, have 1GB RAM, 75 GB disk space and have flexibility to choose the desired OS. Visit Liquidweb