My McAfee has decided to no longer pre-populate my user name when the
laptop starts. Previously I would just have to enter my password and windows
Now it wants a user name and no matter what I try – it does not
work. If I try with user name I have to ring IT support to get me into windows as it locks
This sounds like a question you need to ask your own IT department - whether the previous user name is displayed or not is a setting they can manage. They may have removed your account from that machine.
This is not something that the community is going to be able to help you with - it's your IT team that can assist.