Open the run dialog and type "gpedit.msc", that should allow you to check local policies.
Off the top of my head I can't remember when the policies are stored in the registry, if you can find the key (probably HKLM\Software\policies\...) and remove them manually?
Might be worth checking for browser hijacks / browser hardening software (Spybot etc.).
Group Policy should not be hitting any local users, though a forced removal of a PC from the domain has been known to leave some settings behind. Maybe remove the PC from the domain, delete the machine account from AD, re-add the PC, move the account back to the correct OU, force update group policy (remembering the replication delays).
I usually force the group policy update with the following command "gpupdate /force /boot /sync".
My initial checks would be browser hardening software / browser hijack, then local policy, then the registry, finally the removal from the domain.