Installing different versions of IE
It is a good practice to test your web work in as many browsers as possible. If that browser is Internet Explorer, for sure you’d like to have different versions of IE available. So what can you do about it?
Installing a standalone
A standalone version could be a possible solution. First, you would need to download the version of your choice.
You can find some at:
http://browsers.evolt.org/?ie/win32/standalone
These zip files are ready for downloading and unzipping on your system. Yet, there’s a problem with these files. First, you will only find old versions of IE, up to IE6. That’s a problem if you want to use IE7 or higher.
Also, these standalone versions have some unwanted problems. As an example, conditional comments will not work properly. You do need to download and install file by file if you want to use more than one version.
There’s no solution for the first problem (how to get IE7 or a higher version as a standalone) but Joe Maddalone came with a solution for the second, and this solutions did avoided most of the problems found at evolt’s IE standalone versions. Not only that, but he created an installer that would install more than one version in one go. You can find this solution at trendosoft
Still, there still are some problems unsolved and versions 7 and 8 can’t be found. Ok, IE8 is not a problem as you can get it directly from Microsoft, but testing in a non-existant IE7 may be a problem 
So what can you do now? Look for a better solution, of course!
Virtualization is the answer
Virtualization has some advantages. You can not only have more than one browser installed (the true, original IE in the version you may have downloaded when it firts came out) , but also more than one OS. Therefore, you can experiment with different combinations of OS/IE… which is fantastic because some versions show different problems depending on the OS installed.
And, surprise, surprise, Microsoft has one page where you can download all these images, Operative System included. Of course, you will have first to download and install the software that will allow you to install more than one virtual OS in your computer and its corresponding browser… Virtual PC
After that, simply download the corresponding image and install it in your virtual PC…and Voilà! Now, you can test in various OSes and various versions of IE without further ado.
The only disadvantage is that these images will stop working after a period of time… they are for testing purposes only and they do have a expiration date.
But, hey, this is better than nothing!