Since Internet Explorer 7 is on Windows Update and installed as a high-priority update a lot of users have Internet Explorer 7 installed or you are using the brand new Windows Vista, but how do you do when you are a web application developer and have to test it on Internet Explorer 6. Yes, Internet Explorer 6 will be with us for a long time.
You have three options:
Have a secondary machine stand by with Internet Explorer 6. An easy but expensive solution.
Install IE7 and IE6 side-by-side. Not that easy and not recommended but it can be done.
Use Virtual PC to set up a virtual machine with Internet Explorer 6.
Microsoft is doing a great job with all these new VPC images for us developers and testers so we can test new software, betas and now older software in our own sandbox.