Free, yes absolutely free VHD images of Windows XP with SP2, SP3 & IE6, IE7 & IE8 and also Win Vista with IE7 are available from Microsoft site as free downloads. It is a great way to test websites using different versions of IE.
Internet Explorer Application Compatibility VPC Image
Check the link below for other free VHD images of Microsoft products including Windows Vista, Windows Server 2008, SharePoint Server 2007, ISA 2006 firewall, Exchange Server 2007, BizTalk Server 2006, Identity Lifecycle Manager 2006, forefront and system Center products.