The group client failed logon, access denied

No matter what I do, I cannot log in.  I have Vista Business and it is a personal computer in my office.  I have done the F8 key when it is booting up and I get the screen however regardless what selection I make when it boots up it gives this message The Group Client Failed Logon, Access denied.   I do not have a recovery cd because I purchased this from a windows approved refurbisher.    Can you help me, I really don't know what else to do unless you know of some other key combinations I can use to get past this Group Policy shutdown.  

Thanks Lee