Hehehee - this'll upset a few people.
Here's my reccomendation
1 - Install linux - This is free (as in zero dollars) I personally recommend Ubuntu
2 - Install vmware server - Also free on the Linux platform (you have to pay for the other OS's)
3 - Install as many different OS's and browsers as you need (free if you have a copy I guess)
4 - Test away
🙂 - you can run all your OS's at the same time (might need more RAM if you've got an older machine)
4.5 - If you use php / mysql - install a LAMP stack and use Linux as your development platform. (guess what - also free).
5 - Perhaps even host your own site. (free + easy)
6 - Never have another virus (priceless)
7 - Never have another blue screen (calming)
8 - Be able to leave your computer on indefinitely without having to reboot due to some poorly written process hogging resources (liberating)
9 - Get free updates + support + and os that just 'works' and never have to pay again or replace your PC to run a bloated OS that does little more than look good.(really liberating)
I switched over to Linux years ago for web developing and have never looked back.
The Linux repositories have whatever software you need (yup you guessed it - for free). I even use it within a completely micro$oft environment - it talks to my M$ hosted exchange server (which I retained only to be able to host the push service for WM6 powered phones) I can read / write / edit office documents to communicate with my clients and I have migrated all of my software development to realbasic + eclipse platforms (yup you guessed it - both free).
Linux is not as polished looking as Winoze, but it is much more capable and is the perfect web developing environment.
And best of all
It's FREE
🙂
But if you don't want to take a trip the dark side you can simply install all versions of IE together -
http://tredosoft.com/Multiple_IE
I used to use this when I developed on Windows - works great.
The interfaces are not so good but the rendering engine is the important part.