How to test on IE while developing with OS X?

I'm trying to get my head around how I can test that web apps work on Internet Explorer whi开发者_C百科le developing with OS X.

The following criteria are all important:

• I need to be able test IE6, 7, 8 and 9
• Cost (I want to keep my costs to a minimum)
• Legality (but I don't want to violate any software licenses - from what I can tell I'm going to have to buy at least one Windows license)
• Reliability (i.e. I want to run a "real" Windows/IE instance, not something like ies4linux, etc.)
• Need to run each IE instance of long periods of time (so a shared instance might not be a workable solution)

If Virtual PC was still available for the Mac then the VPC images supplied by Microsoft would be exactly the solution I was after, but obviously without being able to run Virtual PC I can run these images.

Update: I am wondering if my best option is a Windows 7 Netbook + a USB KVM switch.

Your best option is to run the Real Thing (tm) in a VM such as Parallels, VMWare, or VirtualBox. Google around a bit - I think you can migrate an existing VPC image to a newer VM product.