There are a lot of tools around to allow you to test sites in Internet Explorer - among those, Microsoft have provided some virtual machine images for various combinations of Windows and Internet Explorer for free. Here's a few notes on using these VMs, including accessing localhost on your host machine from the Windows guest.
Download virtual machines from modern.ie
To log in the password is Passw0rd! (it's set as the desktop background, but doesn't help if you're booting up an image from ages ago and you've forgotten the password!)
If you have a site running on localhost on your host (main) machine:
To access the host machine, on the virtual machine (guest) visit http://10.0.2.2 or use the host's IP address. To find the host IP, on the host open a command prompt and use
ipconfig (Windows) or
ifconfig (OSX) or
> ipconfig IP address.........: 192.168.0.2
This will almost always start with 192.168 or 10.0. You'll also need the port number - if the site is in IIS, this will be listed on the right-hand side when you have the site selected.
In the VM, visit http://[host ip]:[port] eg
If your site on the host is Windows and IIS you'll need to open the firewall to allow access from the network. Open Control Panel > Firewall > Advanced > Inbound rules > New Rule. Select 'port' and add the port number from IIS; click allow, then select the networks (all if you're not sure).
Other browser testing tools: