Who said that only iPhone users could interact with Instagram? Pixsta is a small application which is a Windows Instagram client which sits in the Windows taskbar.
Pixsta allows you to search for photos, friends, people and download as many Instagram photographs as you'd like and with recent updates, you can also do some customization. It provides real-time notifications from Instagram, allows for commenting and sharing and enhanced searching.
Version 3.0.3.52524 is a freeware program which does not have restrictions and it's free so it doesn't cost anything.
For security reasons, you should also check out the Pixsta download at LO4D.com which includes virus and malware tests. Additional screenshots of this application download may be available, too.