Is there any way to install mobile browsers on Windows 7 to aid development rather than having to test on a mobile device?
Not directly, but there generally are emulators that can give you a pretty good idea of device-specific rendering.
Microsoft have a Windows Phone 7 emulator available for developers - I think this might be the one: http://www.microsoft.com/downloads/en/details.aspx?FamilyID=04704acf-a63a-4f97-952c-8b51b34b00ce . The emulator should have everything Windows Phone 7 has by default, including Internet Explorer.
Note that I don't know anyone that uses Pocket IE. Most people use Opera Mobile, which has an emulator available at http://www.opera.com/developer/tools/