Do some maintenance it is likely just a Windows installer issue, not Apple's and something that happens, which is why backup system restore image, use Windows 7 DVD etc
patch tuesday update is one likely cause
Use CCleaner 3.x and use Registry tool as well as clean up all the temp caches and free up disk space
properties - disk cleanup - system files - remove everything from there too
clean registry again possibly
use 10.7;.4 Boot Camp Assistant and download the current new drivers and install those -
Have you even tried to repair or uninstall what you have now?
Apple leaves a lot of things around that do not get uninstalled and keeps old versions around - Safari, iTunes etc and shared common support files - clean those out - there is a tech note for uninstalling Apple Windows Software.
Not sure what you need or expect from ASU in Windows everything is avialble for manual download and install too. And nothing for Boot Camp through that (there was for BC 3.04 to get to 3.3) but that is old.