There r ways to run different versions of IE on single XP computer…..
Download and install virtual box on XP and take win98 (either install any one IEversion, which differ from current xp’s IEversion) or linux and try ur application on different versions of IE. On linux u have to download IES4Linux which helps to install IE 6, 5.5 and 5
To download virtual Box: www.virtualbox.org/wiki/Downloads
To download IES4Linux: www.tatanka.com.br/ies4linux/page/Installation
U have to try out for IE Collection the link is http://utilu.com/IECollection/
u go for IE Tester. The link is : www.my-debugbar.com/wiki/IETester/HomePage
Download and install Multiple IE runner…. Just search for multiple-ie-setup or link to http://tredosoft.com/Multiple_IE
CAUTION: IF U DO NOT HAVE A VALID EULA FOR ANY “MS OS PRODUCT”, U ARE NOT AUTHORIZED TO INSTALL, COPY, OR OTHERWISE USE THE OS COMPONENTS AND U HAVE NO RIGHTS UNDER THIS SUPPLEMENTAL EULA.
Hope for the best !