ah, so you were in a domain and now you aren't. try logging in again but
this time instead of just your user name use the old domain name slash your
old user name... like domain\username (or is the the other slash?? well
try domain/username if the other one doesn't work) in the user name box and
the old domain password for the password. this 'should' let you in with the
cached domain credentials. you should also be able to login with just the
local machine admin account if you had one. getting you back on the domain
will probably require a domain admin to remove the old machine account and
recreate it, but ask them first before you try anything else.