It's hard to do but these might help,
X-Ray, a bookmarklet to examine elements within the document model, similar to firebug's 'inspect'.
Fiddler, an http debugger for ie 6/7
IE Developer Toolbar, similar in power to firebug but in no way as comprehensive.
IETester, full-blown IE6 standalone browser, finally you can test against IE6 on Vista!
