You can refer this KB http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2058227
Apart from this vSphere 5.5 will not upgrade the window 2008 R2 . But before upgrade you can upgrade to window 2008R2 SP1 .
You can refer this KB http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2058227
Apart from this vSphere 5.5 will not upgrade the window 2008 R2 . But before upgrade you can upgrade to window 2008R2 SP1 .