We are currently developing an application that will have to run on older corporate PCs that still have IE6 installed.
I have been looking around a bit, but I canno
You can take look at Website Docs.
Officially IE7 is not supported. IE8 and IE9 will be support.
Here is the link to the official docs for Bootstrap versions: http://bootstrapdocs.com/
Looking at Browser support for Bootstrap 1.1.0 it says Internet Explorer 7+. The docs for the earlier version v 1.0.0 (which was the first public release) doesn't even mention supported browsers. You can check if more recent version added support for IE6, but I don't think so. I also discourage using an old version at all.
If you can chose another framework I'd suggest YAML, it is actively maintained, well documented and supports IE6, too.